What am I???

[phillie]

I bought an old machinist box and there were 50 or 60 of these in it. They are marked "MONO LOCK". They measure 3" end to end. There are two prongs on either side of a flat piece of metal. When you draw back the bolt the two prongs retract and the flat piece stays in place. Some are copper and some steel.

Thanks

[rusty]

It is a variant of the Cleco wedge-lock clamp. Use it for holding 2 pieces of sheet metal together while wqelding them. (drill a series of holes, stick them in , expand  etc)