Here is a part so common, so anonymous, yet so ubiquitous that most people never think about it until they need it. The 1/4"-20x1" long threaded black oxide pan screw is the most standard size holding your scooter or power chair's armrest to the bracket.

Found on literally hundreds of scooter and power chair brands and models, this humble little screw does so much, yet asks nothing in return but to be tightened down with the correct Phillips blade screwdriver.

⚠ WARNING California Residents: Proposition 65 Warning