Most splices are compression-type splices (crimps). Primer pocket reamers or swagers are used to remove military crimps in primer pockets. Larger ridges produce larger crimps in the hair and smaller ridges produce smaller crimps. The edge with a seam is curved and has about 40 small crimps or folds. These crimps form great frictional forces which keep the joint from seeping. This is a single-hole punch which also crimps a metal fastening loop around the hole. The look is similar to the crimps left after taking out small braids. Likewise, roll crimps are in use for metallic, paper, and plastic hulls. The crimps were well positioned politically to protect their lucrative trade. Non-ratcheted crimps must "never" be used in "mission critical" applications. In 1872, Congress passed the Shipping Commissioners Act of 1872 to combat crimps. Crimps were sent to Germany to recruit volunteers. Some crimps made as much as $9,500 per year ().