1/2-13 bolts have holes drilled in them to be used as bushings. Drill rod inserts are used to line up #40 holes before being clamped with vice grips. Drill rod is removed and #40 hole is drilled out to what ever size (bushing,drill rod) pair is used. Aluminum insert machined to be with of capstrip and also clear spar flange. Threaded for 1/2-13 bolts. Also several holes drilled to help with aluminum shavings while drilling.