Lots of wedges are triangle shapes.
A door lock is a wedge.
You can put a wedge under a tyre to stop a car or a bike from moving backwards.
There are little wedges on bike wheels.
You can put a wedge under a board to make a seesaw.
A wedge is useful to stop a car on a ramp.
When you use the brake on a car, it is like a wedge.