Originally Posted by
cny-bikeman
Thus some of the confusion - whether front or rear they're called dropouts. Rear triangle is what the rear dropouts are attached to, fork for the front dropouts.
I am fairly new to this, so I may not use the right terms. The Sheldon Brown article refers to it as a forkend alignment and Park calls the tool a frame and fork end alignment gauge.
Adjusting bicycle forkends to be parallel