When you hide a homemade shank up your ass and inadvertently shit it out when it gets forgotten about, thus causing the option of loosing your only prison weapon or toilet diving for the lost tool.
"I've got shit up my arm because I shankshat and I got to do over Larry Longbrow in the showers later" or " I got a perforated bowel because I pushed it up too far and couldn't shankshit it out"