I borrowed a friends chainsaw and was putting a new chain on it and this part fell out while I was cleaning the debris out of the chain area. It is about 3/8" wide and 9/16" long. It si round on one end and square ion the other. The square end is only 1/4" wide. The round end has a 1/8" hole in it. I cannot see anywhere, up in there, that it goes?