Do blacksmithing? Got no friends? Then this is for you. Alright, you may one friend but he doesn't want to hold hot stuff for you while you hit it. Here's how to adapt a drill table clamp to make it quick and easy to firmly clamp metal to the anvil using one hand.
Clamp for a drill table
Length of square steel bar to fit your hardie hole (1'' in my case)
Angle grinder (or hacksaw)
Step 1: Cut!
Cut the bolt off the bottom of the clamp and make sure it's flush with the bottom plate.
Cut a length from the steel bar long enough to completely fill the hardie hole. Ensure the end to be welded is clean enough for a good weld.
Step 2: Weld
Weld the bar to the bottom plate. It doesn't have to be tidy, it just needs to be strong.
Step 3: Check
Make sure it fits flat over the hole. If it doesn't, file or grind your weld until it does.
Step 4: Holdfast!
Clamp that sucker down! Get the adjustment done before your item is hot and you will be able to clamp that sucker fast in less than a second using only only your left hand.
It's hammer time.