At the Deluxe Resorts like the Contemporary and Polynesian you can create a code to open it, however I am not sure if the Value Resorts have them or the old safes where you need a key to open them.
We were at POP in August and our room had a key code safe. It wasn't very big, built into the wall near the sink area. It wasn't even big enough to put out laptop into. HTH
Just returned last week from WL, key safes. They are about 3 inches deel and maybe 12 inches square. Just the right size for money and small valuables, just remember where you put the keep, and be sure to retrieve your items and leave the key in the safe when going home.
They are free unless you lose the key! Then you have to pay $25 to get them to replace the key you lost and open your safe.
If you have laptop you want secured, I suggest you buy one of the locks they sell for that purpose (you can get these at Best Buy or on Amazon, there was a recent thread). Or if you are renting a car, put your laptop in the trunk when you are in the parks to keep it safe. Unfortunately, sometimes the mousekeepers prop those doors open when they clean and that can cause a dishonest guest to go right into your room and help themselves! So at the very least, keep your valuables that don't fit into your safe put away. If it takes too much time to find them, it takes too much time to steal them.
It will be stuck right inside the safe lock. If it isn't, call the front desk immediately so they know you aren't the one that lost it! However, the housekeepers probably check that when they clean a room that has been checked out.
My husband always puts the key in his wallet. His wallet has a built in key chain that is perfect for that. And he bought it at WDW!
Here is a picture of the wall safe in our room at Pop. It was big enough for my laptop with room to spare. Ours used a key which was already in the safe lock.