Should slip snugly  in and out BENDING LEAF NOSE GAP Hold bending leaf at the finished  angle of bend 90°(in this case) Scrap of material to be bent Figure 4-141.  Profile illustration of brake nose gap adjustment. Figure 4-142.  Brake alignment with two test strips 3-inches from  each end. Figure 4-144.  Brake alignment by comparing test strips.  Folding a Box Figure 4-143.  Brake alignment with two test strips bent at 90°.  A box can be formed the same way as the U-channel described  on in the previous paragraphs, but when a sheet metal part  has intersecting bend radii, it is necessary to remove material  to make room for the material contained in the flanges. This  is done by drilling or punching holes at the intersection of  the inside bend tangent lines. These holes, called relief holes  and whose diameter is approximately twice the bend radius,  relieve stresses in the metal as it is bent and prevent the metal  from tearing. Relief holes also provide a neatly trimmed corner  from which excess material may be trimmed.  the other; they should match.  [Figure 4-144]  If they do not  match, adjust the end with the sharper bend back slightly.  4-72