This item was originally created by @Bonus_Action on Instagram! This is not my design in any way whatsoever.

Chalk One Up: As an action, you can use this chalk to draw a simple symbol. A creature using this chalk must have at least an intelligence of 8. You can draw up to 20 symbols with this chalk before it is completely used up.

Square: Drawn around a lock, grants +5 bonus to Dexterity (Slight of Hand) checks to unlock it.
Circle: Whilst standing in the circle you have advantage on Wisdom (Perception) checks you make to spot traps.
Triangle: Summons and spreads caltrops in a 5ft radius.
Cross: Drawn on footwear, grants +3 to stealth checks for 1 hour.