Round Base T-nut has internal Thread and is used to install climbing holds.
Before installing holds we must prepare our wooden board first. We drill holes in the board with a diameter of about 1.20 cm. Make holes in places where you considerate to put climbing holds. We drill in places where we will consolidate holds or create a grid of holes. With the basic grid you can change positions of holds later more easily. If you know in advance that you will never move holds, the grid isn´t necessary.
Fasten climbing holds with allen screws and wooden screws. to find out suitable size of allen screw you have to put the screw throught the hole in climbing hold. If the screw sticks out on the board thickness you´re good. Internal thread of t-nut and external thread os allen screw must fully overlap. It´s wrong if threads meet partially or not at all.