Pre 1963 6 cylinder Chevrolet engines had slotted screws for the valve cover, tappet side cover, timing cover and oil pan. They were commonly called stove bolts. I have the same socket in the Proto brand. The sleeve around the slotted screwdriver bit kept the bit centered on the bolt. I spent 40 years studying, repairing, rebuilding and hot rodding 6 cylinder Chevy 235 and 261 engines. I got real sick 9 years ago and sold 22 engines and all the hot rod speed parts and only kept the tools for working on them.
EvilDr235