Screw-on T-Nuts for climbing holds with three holes
POWERTEC QTN1108 Screw-On Tee Nut, 5/16” x 18 (8PK), Zinc Plated Carbon Steel for Indoor/Outdoor Use - Screw On Flange T Nuts for Non-Rotating Fastening in Your Woodworking Shop - Amazon.com
M8 M10 Round Flat Base T Nuts 3-Hole Tee Furniture Nut Screw Color Zinc Plating | eBay
Tee Nuts (25 Pack) - Maker Store USA
Screw - 1 Phillips Pan Head w/ Matching T-Nut - 609722160162