Keys

Keys are valuable items that allow for, you guessed it, the unlocking of things. Keys may be double clicked  from inventory, or clicked once to select, then the "use item" button can be pressed.

Keys may be rocks, small hammers, shovels, clues, pieces of items, or actual keys. Keys are capable of being used more than once, or being consumed after use. The same key may be used multiple times on one door, but may be consumed at another, so be careful.