There are a number of different methods of forming  joggles. For example, if the joggle is to be made  on a straight flange or flat piece of metal, it can be  formed on a cornice brake. To form the joggle, use the  following procedure:  When a joggle is necessary on a curved part or a curved  flange, forming blocks or dies made of hardwood, steel,  or aluminum alloy may be used. The forming procedure  consists of placing the part to be joggled between the two  joggle blocks and squeezing them in a vice or some other  suitable clamping device. After the joggle is formed, the  joggle blocks are turned over in the vice and the bulge on  the opposite flange is flattened with a wooden or rawhide  mallet.  [Figure 4-163] Since hardwood is easily worked, dies made of hardwood are  satisfactory when the die is to be used only a few times. If  a number of similar joggles are to be produced, use steel or  aluminum alloy dies. Dies of aluminum alloy are preferred  since they are easier to fabricate than those of steel and wear  about as long. These dies are sufficiently soft and resilient  to permit forming aluminum alloy parts on them without  marring, and nicks and scratches are easily removed from  their surfaces. When using joggling dies for the first time, test them for  accuracy on a piece of waste stock to avoid the possibility  of ruining already fabricated parts.  [Figure 4-164]  Always  keep the surfaces of the blocks free from dirt, filings, and  the like, so that the work is not marred.  Lightning holes are cut in rib sections, fuselage frames, and  other structural parts to decrease weight. To avoid weakening the member by removal of the material, flanges are often  pressed around the holes to strengthen the area from which  the material was removed. Figure 4-164.  Samples of joggled metal. Figure 4-163.  Forming joggle using joggle blocks. Clamping device Material being joggled Joggle block Joggle block Wooden mallet Bulge caused by forming joggle STEP 1 Place material between joggle blocks and  squeeze in a vice or other clamping device. STEP 2 Turn joggle blocks over in vice and flatten bulge with wooden mallet. Lightning Holes 1.  Lay out the boundary lines of the joggle where the  bends are to occur on the sheet. 2.  Insert the sheet in the brake and bend the metal up  approximately 20° to 30°.  3.  Release the brake and remove the part. 4.  Turn the part over and clamp it in the brake at the  second bend line. 5.  Bend the part up until the correct height of the joggle  is attained. 6.  Remove the part from the brake and check the joggle  for correct dimensions and clearance. 4-82