mack the knife
Putting on a condom. Also called 'mack the badger' because it feels like you're being attacked by a badger. You do it when you're about to do something messy.
"I macked the knife before I went to bed. I didn't want to get caught in the act.", @SexLifeIsMessy
"Macking the knife is like preparing for a war. You don't want to get caught off guard.", @CondomGuru
"Mack the knife is just a fancy way of saying 'I put on a condom.'", @BadgerFanatic