Your method of attaching leg holds to leaning logs

So they stay until the catch

Tie wire. Use a single wrap so that the critter will tear it loose when caught. I think there is archived leg hold trapping marten info in the Wilderness page.

3 nails or you could use real light wire and wire in place,I think nails works better,good luck.

Tie wire here. Twisted under the pole. Marten will get it pulled out and be hanging by the trap chain. IMO 120s are lot better

Next Year I'll have more Belisle 160's and 220's

It's Foothold

#1 choice for me, 16g. wire with a piece of surveyors flagging tape on it so you can find it when they knock it off the trap. Half a twist is perfect for most small animals. Doubles as a attractor.
(Mad Mike mentioned this above)

#2, Plain old string. Works good, biodegradable, can tie it hard to the tree so it's there after the catch and can be reused. They don't break it they wiggle the trap off of it, usually.

#3, Plain surveyors flagging tape, but it breaks easily in extreme cold temps. Cannot reuse it, have to pick it up after each catch as it is litter, sometimes it doesn't break when you want it to. Last choice, when I am out of the other two above.

#4, a couple of cuts with an axe or machete to put a slice in the tree to hold the trap, sucks, but better than nothing. Never use this anymore. Don't run out of wire, flagging or string.

Nails work, but I like smaller diameter poles and those are hard to put nails in they are so small. Work great on bigger poles or other sets. I use them for conibears but this question was for footholds.