Twisted 29g or triple twisted 30g. I actually was able to get some MM wire in there, but it was not easy. The screws can capture big wire, it's just the space between the screw & top cap you have to be careful about. TINY deck, but definitely the easiest tiny deck to build on... I position the coil between the posts, close to the edge of the deck, and then put both leads on the inside of the posts and wrap the wire all the way around so they face the inside of the deck. Never had a short that way (*knocks on woodvil*
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