(2024 rules) Does Expertise in Sleight of Hand give any benefit to picking a lock?

I say yes. Sleight of Hand is essentially finger work. What does lockpicking need? Delicate finger work. I generally say that all lockpicking checks are sleight of hand. It’s the only skill that makes sense in this case. Therefore, expertise in sleight of hand would let you get better at picking locks.

As Smite, the Wise Paladin, once said:

Quote from SmiteMakesRight_3_5 >>

[...] In 3rd edition D&D, there were what was known as "crossbow rules". Crossbows needed to be reloaded between attacks and what that meant was described in the description of crossbows instead of with other weapon properties even though it applies to other weapons. Other rules where a broader rule was buried in an obscure place were then called "crossbow rules". In 5e, picking locks with Sleight of Hand is one such crossbow rule. Sleight of Hand says it used to "Pick a pocket, conceal a handheld object, or perform legerdemain". Where do we know it's used for picking locks? Thieves Tools tells us the DC (15) but not the associated proficiency. In the Lock entry, it tells us we need Thieves Tools and a DC 15 Sleight of Hand check. Now, does this apply to all locks? Maybe. [...] 

I think the only exception might be a broken lock, which you have to ram your shoulder through or something similar.

Quote from LinkArcher >>

I think the only exception might be a broken lock, which you have to ram your shoulder through or something similar.

In that case, you are no longer picking a lock. A crowbar or carpenter's tools would be more helpful than delicate thieves' tools.

Quote from Davyd >>

I would say that Expertise counts as Proficiency for the purpose of determining if you have Advantage on an ability check using both a Skill Proficiency and Tool Proficiency.

I'm not sure I agree with that as a general rule tbh. 
If you have a feature that gives you Proficiency with a certain skill then you have said proficiency. If you have another feature that gives you Expertise with that skill then you have expertise. But having expertise does not nullify you having proficiency so you would still qualify for getting Advantage on the Tool check.

However if there happens to be a feature that gives you expertise without giving you proficiency (AFAIK there is none currently) then you would not automatically also have proficiency (AFAIK it only matters for tool checks). It is a strange hypothetical edge case that I hope the designers doesn't create an actual case of.

Quote from LinkArcher >>

I say yes. Sleight of Hand is essentially finger work. What does lockpicking need? Delicate finger work. I generally say that all lockpicking checks are sleight of hand. It’s the only skill that makes sense in this case. Therefore, expertise in sleight of hand would let you get better at picking locks.

Except that is not what the rules say. Having Expertise in a skill doesn't matter for a check using a tool, having Proficiency in the skill is what gives you advantage on the check. And then being proficient with the Tool is what allows you to add you proficiency bonus to the check.

Now if you had expertise with the tool then that would matter but AFAIK there is no way of getting that in the 2024 rules.

Quote from Thezzaruz >>

Quote from Davyd >>

I would say that Expertise counts as Proficiency for the purpose of determining if you have Advantage on an ability check using both a Skill Proficiency and Tool Proficiency.

I'm not sure I agree with that as a general rule tbh. 

Here you go:

Expertise is a feature that enhances your use of a skill proficiency. When you make an ability check with a skill proficiency in which you have Expertise, your Proficiency Bonus is doubled for that check unless the bonus is doubled by another feature.

So, Expertise itself is the general rule that says Expertise modifies Proficiency. 

Quote from Thezzaruz >>

However if there happens to be a feature that gives you expertise without giving you proficiency (AFAIK there is none currently) then you would not automatically also have proficiency (AFAIK it only matters for tool checks). It is a strange hypothetical edge case that I hope the designers doesn't create an actual case of.

If you could somehow have Expertise without proficiency, your bonus would be two times 0 (see quoted rule, above). Having Expertise without Proficiency doesn't actually do anything.

Quote from Thezzaruz >>

Quote from LinkArcher >>

I say yes. Sleight of Hand is essentially finger work. What does lockpicking need? Delicate finger work. I generally say that all lockpicking checks are sleight of hand. It’s the only skill that makes sense in this case. Therefore, expertise in sleight of hand would let you get better at picking locks.

Except that is not what the rules say. Having Expertise in a skill doesn't matter for a check using a tool, having Proficiency in the skill is what gives you advantage on the check. And then being proficient with the Tool is what allows you to add you proficiency bonus to the check.

Now if you had expertise with the tool then that would matter but AFAIK there is no way of getting that in the 2024 rules.

This does seem to be an issue at first glance, but the way in which it is worded actually solves this problem.

If you have proficiency with a tool, add your Proficiency Bonus to any ability check you make that uses the tool. If you have proficiency in a skill that’s used with that check, you have Advantage on the check too.

This above text establishes the rules for using tools.  But there are already rules elsewhere which establish how to resolve ability checks which involve using a skill.  These two sets of rules are both applied simultaneously.  One does not supersede the other.  They both apply.  

Skill Proficiencies

Most ability checks involve using a skill, which represents a category of things creatures try to do with an ability check . . . The DM has the ultimate say on whether a skill is relevant in a situation.

If a creature is proficient in a skill, the creature applies its Proficiency Bonus to ability checks involving that skill. 

At the same time, we also have this rule:

The Bonus Doesn’t Stack

Your Proficiency Bonus can’t be added to a die roll or another number more than once. 

. . .

Occasionally, a Proficiency Bonus might be multiplied or divided (doubled or halved, for example) before being added. For example, the Expertise feature (see the Rules Glossary) doubles the Proficiency Bonus for certain ability checks. Whenever the bonus is used, it can be multiplied only once and divided only once.

So, if your ability check uses a certain skill in which you have expertise, that ability check adds double your proficiency bonus.  That always happens by rule.  There is no scenario where that doesn't happen.

Next, the rule for Tools begins by describing that there are some benefits to having proficiency with the tool, such as adding the proficiency bonus.  But, we know from above that this bonus cannot be added more than once.  This just provides another way in which it might be added if it's not already being added.  Then, once it is established that you have the Tool proficiency, if your ability check also is one that uses a skill in which you have proficiency (which means that you are also already applying the other rule to resolve that fact), then an additional benefit is that you have advantage on the roll.

So, you apply the Skill Proficiency rule to add the Proficiency Bonus.  You apply the expertise rule to double that bonus.  You apply the Tool Proficiency rule to add the Proficiency Bonus -- but you also use the Bonus Doesn't Stack rule to avoid actually adding it twice.  Finally, since both of these proficiencies exist for the same roll, you get advantage on that roll.

Quote from cl0ud_stalker_234 >>

isn’t the slight of hand just for an example skill?

 If you look under the "Lock" item description, and "Opening a Locked Door" section, they tell you, explicitly, that you may attempt to pick the lock, but to do so requires the use of thieve's tool, and a Dex(Sleight of Hand) d20 test.  There no "rules" for what skills go with what tools, so it is up to the DM's discretion, for the most part, but there are specific examples where a task requires a tool AND a skill.

I prefer the skillset from 3.5e.  The books actually had full descriptions for the skills, and preset DCs baked in, with tools granting bonuses to skill checks(which were a thing back then).  Also, there was much more variety available for skill based rp.

boo

Remember, folks.  When multiple bonuses are applied to a roll, and those bonuses are not allowed to stack, you ALWAYS use the HIGHER bonus.  In the case of picking a lock, expertise in Sleight of hand grants a higher bonus(2xprof) than that granted by proficiency with thieve's tools(1xprof).  Therefore, the doubled proficiency from expertise in Sleight of hand would be used, at advantage with thieve's tools proficiency.

Yes. That’s what I was trying to say. If you have expertise in Sleight of Hand, you have expertise in Thieves Tools.

Your Proficiency Bonus can’t be added to a die roll or another number more than once, with or without Expertise.

Quote from LinkArcher >>

Yes. That’s what I was trying to say. If you have expertise in Sleight of Hand, you have expertise in Thieves Tools.

This isn't quite accurate. If you have expertise in in Sleight of Hand, you have expertise on the Sleight of Hand skill check to pick locks with Thieves' Tools. If you make a check using Thieves'' Tools and another skill, your Expertise in Sleight of Hand does not apply.

I suspect you were aware, but I wanted to address the phrasing.

It is an important distinction. lets say there is some magical trap the DM may decide the relevant skill is arcana, or if investigating a lock to determine if it had been picked recently it would be investigate/thieves tools etc. And I'm sure there are other uses with thieves tools people come up with that might align with a different skill. i suspect slight of hand will be the go to for 99% of them though as its a fairly narrow useage tool. 

Tool checks are a bit weird as they are rhe only check dependent on 2 things: whether or not you are proficieng in the SKILL and whether or not you are proficient in the TOOL.

The tool check is always based on ABILITY / SKILL / TOOL.

If you have no proficiency in skill or tool, you roll a d20 and add ABILITY modifier.

IF you have proficiency in SKILL -or- if you have proficiency in TOOL, then you also add PROFICIENCY BONUS.

if you have proficiency in BOTH, then you add PROFICIENCY BONUS, but you also roll with ADVANTAGE.

if you have EXPERTISE in skill, and proficiency in tool, then you add double proficiency bonus -and- the roll is at advantage.

Quote from SmiteMakesRight_3_5 >>

Quote from LinkArcher >>

I think the only exception might be a broken lock, which you have to ram your shoulder through or something similar.

In that case, you are no longer picking a lock. A crowbar or carpenter's tools would be more helpful than delicate thieves' tools.

 The DMG includes this suggestion (Common Doors):

With the Utilize action, a creature can try to force open a door that is barred or locked, doing so with a successful Strength (Athletics) check. The table provides the DC of the check. For bigger doors, double or triple the Hit Points and increase the DC of the check by 5. [...]