Katy, many of the cupboard/drawer locks are like that anyway! They allow the drawer to be opened just enough to get fingers stuck in there.
Like bec said they learn really quickly where they are not allowed to go in if they are consistently ltold and redirected. I don't have enough cupboard space to give one over to DS but he does have his own cooker in the kitchen and a box full of kitchen toys to go with it.
I've found that at each developmental stage he will re-test the rules on everything so at the same time, or just after, a bout of SA there is also a phase of doing all the stuff he knows he shouldn't, just to see if those rules remain the same. It's at those times that you need to be consistent again if your LO re-tests the way mine does.