Brake wear sensor?

[GasLizzard12]

This came off my right rear caliper, i have no idea where it goes or how to put it on.

 

[AlpineAccess]

Yep, it sure looks like a wear indicator. It touches the rotor and makes a screeching noise when your pads get low enough. It clips onto the top edge of the metal backing on the side of the pads.

 

[Trunk Monkey]

 

[2001LC]

That pad indicator is worn-out. Time for a new one.