This upgrade to the Thief Blade requires you to be to the Serrated Blade level.

A small grappling hook is housed in the hidden blade and is fired to a distance of 30 feet.  The Grappling Hook upgrade removes the reduction in movement speed based on climbing because of the spring gear helping to re-spool the wire.  You may also make a ranged attack with the Grappling Hook upgrade to a range of 20 ft.  On a successful attack, the target must make a successful DC 15 Strength saving throw or be pulled 10 ft. closer to you.  The target is then Grappled by your hook and must succeed on a another Strength saving throw before they can break free of the hook.

Using this Upgrade on a Thief Blade does not require a new blade but simply having it in your inventory allows for the use of it's ability.  If your Serrated Thief Blade previously had the Poison Upgrade, this Upgrade does not remove it.

Notes: Ranged Weapon Attack: Force, Grappling Hook Upgrade requires the Hook, 30 ft. of Wire of the DM's discretion, Wire Spool and a Strong Spring. It requires a Skilled Tinkerer to assemble it.