laying out the position of the t-nuts that will be embedded in the upper tenon to receive bolts from the head block. the truss rod slot is slightly off center in the tenon due to the asymetry of the cutaway. i ground off one side of one of the t-nuts to allow it to be placed inside the tenon's edges. a scrap of wood is shown in the widened end of the truss rod slot - to eliminate tear out when cutting the slot and also to allow clamping of the tenon when drilling and pressing the t-nuts into the tenon.