Joined: Dec 11, 2009
Posts: 794
Location: Dyer,Indiana
Joined: Mar 08, 2010
Posts: 1934
Location: Northampton, UK
I think it's one of the numbered keys, either 3 or 4 for gadget 1 and gadget 2.
You get 2-3 mines at the start and you can replenish so long as there's ammo nearby. And the mines stay until they're destroyed even if you die.
Joined: Jan 22, 2010
Posts: 457
Location: Detroit, MI