#10 stainless, 1 3/4" long, install until flush. As Cutter expained, a slipping mat is dangerous when a horse looses its footing. Definately silly

If you have a trailer with thin, less dense mats, you might want to use different attaching hardware. Instead of #10 counter sunk 1 3/4" long screws, purchase #10 stainless round head screws 1 1/2" in length. Aso purchase an equal number of the larger stainless "fender" washers, and place one under the head of each screw.

When the pilot holes are drilled for the screws, place them about 4" inside the mats' outer perimeter. These revisions will lessen the chances of the screws being pulled out of the lighter weight mats.

The bed liner material would probably be as slippery as the sealant and isn't made for wood applications, so bonding might be an issue. A rubberized type of roof coating like an elastomeric product would offer a more"sticky" surface, but I don't know how much friction it would have when it becomes wet. I wonder if the sandpaper like, non skid material used on steps, could be bonded to the flooring with polyurethane construction adhesive?

The srews could be installed in a couple of minutes. Only the two fasteners on the butt end have to be removed, and the mats rolled to the head side, whenever it's necessary to flush under the mats. A battery powered drill can remove the screws in seconds. The mat can't move when it is physically attached.

I've never had mats that moved, and if they're cut to size, wonder how far out of place they can migrate?

..... You going to "un-tack" those mats everytime you clean out that trailer? If I had mats that migrated as you say, I would do away with them and bed heavily with pine shavings.

If you want to entirely stop messing with the mats, grab your pneumatic roofing nailer, insert a new roll of 1 3/4" nails into the magazine, and fire them all off around the perimeter of the mats. The entire 120 nail roll per mat is a good start.

Then, because you're not really sure these will hold, grab your 21 degree, full head, pneumatic framing gun laying on the work bench. Crank up the compressor's regulator to a comfortable hundred PSI or so, grab three or four clips of 3 1/4" nails, and go back to the mats. Shoot at least one nail between each of the roofing nails you previously installed, and then another clip anywhere else you choose, just because it feels so good to shoot the gun.

When you have finished installing these nails, and again because you're still not sure if the mat will stay in place, grab your 24 oz framing hammer and crawl under the trailer. You will see the tails of all the framing nails you shot, sticking down through the wooden flooring. With your hammer, bend each one upward until it's flush with the bottom of the flooring. If you don't, all your barn cats and small dogs will have tracks in their fur that will resemble  Mohawk hair cuts.

Now you can be reasonably certain that the mats won't move enough to bother your horses' footing.

LOL!!!!

Seriously, my aluminum floor is really slippery, but my mats don't move at all.  They are heavy stall type mats that are cut to fit the floor and have only about 1/2" of play from side to side/front to back.

I also have a wood floor in my other trailer - super slippery as well.  The heavy mats in there don't move either - they are also properly fitted to the corners/angles of the floor.  And the horses that go in that trailer are quite an active bunch.

Would a thicker mat help?

Ha Ha! Glad you're back, Gard!