What is needed.
All treated lumber:
1 10ft 2x10" cut in half.
1 8ft 2x6" cut in half
2 8ft 2x4" cut in half
1 8ft 1x6" cut per inside measurement of trap
1 8ft 1x4" cut per inside measurement of trap
1 16ft 2x2" cut to four 4 ft pieces
1 4x3 20ga. sheet metal
4 carpet runners from Lowes cut to 38" each (comes in 3 ft width)
1 tube of liquid nails
I used 2" and 3" deck screws
Cut notch out of top of 2x10" boards to allow the four 2x2"s with the carpet runners attached to rest on top.

Attach 2x6s" to 2x10s" for the legs.
Attach two 2x4s" across the bottom of the 2x10s" for support.

Place 3x4 20ga sheet metal with 4ft section as width placed just below the notches cut out of 2x10s. No need to have sheet metal behind the four 2x2s". It just needs to be behind the carpet runners.
The sheet metal will bow, so I drilled in the four corners of the metal, holes which would line up with the edge of the 2x10s. Screw a deck screw in each corner and then with a 2x4, place it across the top of the metal to square the frame up. (It does better to have the Trap standing to keep the metal from bowing. Place another 2x4" at the bottom of the metal. Drill holes in the metal and screw into the top and bottom 2x4s from the inside of the trap, and drill holes on backside of metal to drill into the 2x10s.
I used a staple gun and attached the carpet runners to the 2x2"s. I placed 2 on the far right side, and 2 on the far left side. Alternate each, ie. far right, far left, far right, far left.

Place carpet runners in the slot, and measure across the frame to get the width of your trough for the 1x6s". Place in a V to catch the shot. I also added a 1x4" on the top of the outer 1x6 to make a taller lip. Though difficult, I screwed the deck screws from outside the 2x10s into the side of the 1x6's. Just go slow and watch for the head of the screw coming through the wood to make sure it is aligned to enter the 1x6s.

Use the liquid nails to close in the gaps of the v bottom, and where the sheet metal makes contact with the inner 2x10s


Thickness of the mats compared to a #9 TSS shot.

There are 4 mats. Two per side, one per 2x2.
I know I didn't cover all the details, but hopefully this will suffice.
God Bless,
David B.