A guide block to drill guide holes in the plastic blocks for the slider frame aft pins. This is tool is for the Bill Duffy slider canopy installation procedure, a multiple builder. Drill the canopy guide blocks firstly then set the canopy in position. His words "Best fitting canopy yet, the blocks are great, pins slide in perfectly." Made out of ASA plastic. If you would like to talk to Bill and be enlightened about sliding canopys, give him a call at: 513-304- zero two nine four.