These new and improved thumbscrews allow for tool-less adjustment of tabs when using the squares. They feature a knurled grip on the outside and a 3/16" hex head on the top. The head is 1/2" in height and 5/8" diameter. Threaded portion is 1/2" long with 1/4-20 threading.
Bought enough to replace the socket head screws on my Mega squares. No need to use hex tee handles anymore.
Great when you only have one hand free to make adjustments.