Using Keys

I know this is probably extremely simple to do, but how do you make it so when a gate is locked (invulnerable) and a unit with the key in its inventory approaches it, it opens?

Thanks ahead of time for any help that anyone can give me :]

This should pretty much do it. Its ofe the top of my head

You can also use "A Unit Enters Rect" and make a rect where the gate is. Many older maps did that, but I'm pretty sure that TheSecretarts' way is more efficient.

Ok, thank you

I suggest making a special effect at the position of the gate or person using the key too to make it look awesome, not just some gate opening. And play that gate sound at it too, somewhere in the interface sounds or something like that. Doing things like that should really spice up your map.