Patent for a new and improved nut lock. This design utilizes "[t]he combination, with the bolt having a longitudinal groove therein, and the nut having a circular recess in its inner face and a series of perforations in its outer face, of the key having its inner end bent at right angles and fitted in said recess, and provided with an arm and pivoted catch at the outer end, which catch is adapted to engage with a perforation in the nut" (lines 47-55).