Obholz

As Obholz the part of a rafter called, which remains available after the cut or cut-out of the claw. The claw is used to attach the rafter to the purlin .

There are three types of measuring Obholzes: the horizontal, the vertical and right angle. Of these three types, the right-angled is the most important and most common. The rectangular distance from the top of the rafter to the lowest point of the claw is measured. In a valley rafters or hip rafter the Obholz is also measured from the ridge line or valley line of which indicates the exact intersection of the subsequent roof surfaces in the plane of the upper edge of the rafters.

This dimension is important because the rafter is a structural timber, it has to carry a load. As a rule, the rectangular obholz should be 3/4 of the rafter height. This value should not be less than 2/3. If this rule is observed, the rafter is usually stable enough to carry the load to be dissipated.