Amazon.com: NGe M6 x 10mm T-Nuts, 4-Prong Tee Nut Fasteners, Pronged Tee Nut for Wooden Furniture and Climbing Hold, Pack of 100 : Industrial & Scientific
Stainless T-Nuts, 1/4"-20 Inch, (25 Pack), Threaded Insert, Choose Size/Quantity, by Bolt Dropper, Pronged Tee Nut. (1/4"-20 x 7/16"): Amazon.com: Industrial & Scientific
Metric T Nuts - Zinc Plated Steel
POWERTEC 1/4 in.-20 x 7/16 in. Pronged Tee Nut (50-Pack) QTN1113 - The Home Depot