Lock Joint syringe

Lock Joint syringe is a type of ammunition in Fallout 4.

Gameplay
The Lock Joint syringe is a small dart used only in the Syringer. Unlike most ammunition in the game, it is located under the "AID" section of the Pip-Boy menu, as a consumable, and has a small amount of weight. Enemies hit by the syringe have a chance of becoming paralyzed for 10 seconds. Paralyzed targets will freeze in whatever position they are in, typically falling over, rendering them vulnerable to any attack until the effect wears off.

Locations
It can be crafted by the Sole Survivor.