How do you make your boxes making some 7x7 x12 wood .or would 24 inches be better.

Mine are 16 inches, I don't know why. Got about 20 of them. Have caught many skunks in these with #120 Victor's

If I were to build boxes for skunk I don't think I would go to deep. I would say anything 12 - 16 inches would work fine. Maybe use 120 or 160's.

I have taken plenty of skunks in regular sized marten / mink boxes with a 120 sized trap and 14-16 inches deep.
That said our skunks are not overly huge sized like those prairie skunk.

With a shallow trap and a 120, get ready for getting coons by the hand. I’ve got a few coon by the neck with 120s in deep boxes though. I usually use a 160 or 180 in a regular coon pail or box if I’m going to set a BG. I think trigger set up for skunk is pretty important too. I do about a 2.5” spread but not in the classic “V”. Kills em fast, but they usually do drip a tiny bit when they expire.

Shakey, unless you use a belisle or other zero closure coni the coons pull the paw right out as long as it's staked good.

Here, with what coon was paying for years, thats what I was going for.

If I was to want to trap coon and skunk in those boxes id probably step it up to a 160 coni and a different trigger configuration.

I believe all your conis have to be zero close approved so you don't have the same options.

My skunks aren't huge either like the Midwest and other areas. The 120's do a great job on our size skunk

Very true TD. There's a bunch of different BG's on our certified list but all I use are Belisles. If there's coons around (and there always is) and a hand catch is possible, I treat it as a restraining trap and our min72hr check law comes into play. To remedy this, I make my sets appropriately unless I know I'll be heading to the shack every couple days.

Only time I've ever intentionally set for skunks, I just use one of my marten boxes set on the ground with a 120. Works very well in my limited experience. My marten boxes are 16" deep. TD, 16" is a good size because you can get three lengths crossways out of a 4x8 sheet of plywood, with no waste. Probably why yours are 16" also.

To add to this...120 and 155 traps need a swivel or two for what Turtledale and Shakey touched on....'coon reach ins

That's what it was lol. I knew there was method behind my madness.

I say make the boxes 20”-24” long to avoid coon reaching in,

Les I think coon are going to reach in no matter how long the box is. I guess if you use a body grip pan it might lessen the leg catch rate. But it's not going to lessen reach ins.
If I were trapping skunks, I would make my boxes 10" long with no bottoms. Skunks aren't reachers so no need to make the box any longer.

I use newspaper tubes with deep slots and 120's, and stick the business end into a culvert. Trying to avoid coon. I am trapping skunk before coon are primed up. Last year my little skunk line produced 60 skunk and only 3 coon.