On my trailer I've got bolts holding the T+GV wood sides to the frame.
The bolts have shallow slots in the domed head. I can't get enough
purchase on some of them to get them out. I'm sure I remember
something called a reverse tap from when I worked in a tool shop
40 years ago. You drill a pilot hole and you screw this tap in anti-
clockwise, so when it stops drilling into the bolt, it starts
unscrewing
the bolt. Can anyone confirm or give me the correct name for it?
Thanks,
Pete