Standard size T-Nut for 3/8" x 16 thread climbing hold bolts. 4 prongs hold the t-nut in the wood when you pound it into place.
Choose Zinc for most uses, Stainless for outdoor/wet installations.
Use a 7/16" bit to make holes for pound-ins.
Use a 9/16" bit for screw-ins.
Seating: Once you've pounded them in from the back, you should tighten a hold with a bolt from the front to better seat the t-nut prongs in the wood.
Notes: Screw-in T-Nuts are better and more secure but Pound-Ins can work ok for most wall situations if they are properly installed. We do not currently have Stainless Steel Screw-In T-Nuts available, so if you need Stainless you'll need to get these.
Please use relevant PPE when installing these t-nuts including, at a minimum, eye protection and ear protection!