Plastic-head thumbscrews with hex drive speed up securing and loosening components on an optical table or breadboard.  The large 3/4in (19mm) diameter thumb wheel allows for quick hand tightening of optical components which once in place can be better secured with built in hex drive.  US 1/4-20 and metric M6 versions are available for quick use on the optical table as well as smaller 8-32 versions.