It says it's for last ditch use when you're out of pistol ammo.
Pretty sure I'll be clubbing the fuck out of whomever with my glock instead of attaching a little knife to the empty mag.
Watching him stab the door makes me laugh, since I don't think that range of motion will work with the slide back, when the weapon is empty.
And I'm pretty sure if my slide is mag that magazine is going on the ground.
Has to be a joke.