Boilers may be repaired by placing a hard or soft patch on the defective part. For a hard patch, the defective part is cut out, rivet holes are drilled or punched around the opening, and the patch is applied and calked. A soft patch is made by placing a piece of boiler plate over the place that threatens to give way. The plate is held in place with 5/8 or 3/4 in. countersunk screw bolts. A piece of sheet packing covered with red lead is often put under the patch, or the red lead is used alone.