Do Springlock suits exist?

These devices actually exist in real life. Springlocks can be used to firmly hold various things back in a certain position. This is the use that is relevant to FNAF. In FNAF, Springlocks are used in the uncreatively named Springlock Suits.

How painful is a Springlock failure?

The springlocks holding it back are also very dangerous and will slice through your neck and stomach making it impossible to scream for help, you are left to die in the suit. It is painful, there are spikes impaling your body in every place and it will take a long time for you to die.