The bottom part slides up and down the middle post of the top part. When the cuff is on snuggly, a padlock is passed through one of the rounded holes in the middle post, as close as possible to the bottom part to secure it. These cuffs will also work well on ankles. The large hole in the end of the post can be used to attach to a chain belt or lead. Supposedly made by Scott Rich, a blacksmith in Oakland, CA, two or three years ago.