This jig prevents cleavage of the mortised member but does not prevent crushing of the shoulders of the mortise beneath the cross pin.
Loads were applied to the mortised member of the joint through two lengths of steel channel.
Presumably, the wider the shoulder, the greater the pin diameter, and the higher the compression perpendicular to the grain of the mortised member, the greater the resistance to crushing beneath the cross pins.
In the case of the 2-inch yellow-poplar tenons with a 2-inch end-distance in 4-inch-deep mortised members, substantial crushing of the mortise walls occurred with both the 0.
In a few specimens, crushing was noted beneath the cross pin on one side of the mortised member without the occurrence of crushing on the other side.