This T-Handle Hex Driver by Flying Gyroscope holds any 1/4″ hex drive bit, with more leverage than a screwdriver but less than an impact driver. It is modeled and printed in two halves, then tiny knurled brass inserts are heated with a soldering iron and pressed into the soft plastic. The plastic cools into the knurls, leaving a fairly strong threaded nut that can accept a bolt from the other side. I printed this first in ASA and then NylonX.