Most Sentry safes use wafer tumbler locks as key entry locks. A wafer tumbler lock uses flat wafers to prevent a central cylinder from turning. To pick this type of lock without damaging it, all you need are two common lock-picking tools that can be fashioned from everyday household objects: a lock pick and a tension wrench. Any stiff, thin piece of metal, such as a paper clip, can be used as a lock pick. Any stiff, thin, flat piece of metal, such as a hairpin, can be used as a tension wrench.
Examine the key. If the key is flat on one edge, it is a single-sided wafer lock. If it is ridged on both edges, it is a double-sided wafer lock. If you do not have the key, place the lock pick inside the lock. Press downward. If you hear a clicking noise or feel tension, that means the lock is a double-sided wafer lock.
Place the tension wrench inside the keyhole and turn the keyhole slightly until it won't turn anymore. Hold the keyhole in the turned position with the tension wrench. That causes the cylinder to press up against the wafers. The cylinder is the main component of the lock that is turned by the key.
Insert the lock pick into the key hole as far as it will go. Angle it upward so the tip is against the ceiling of the keyhole. Drag the lock pick back and forth against the ceiling of the keyhole. That is called "raking." Raking will push the wafers out of the cylinder. When they fall back down, instead of going back into the cylinder, they will be caught on the outside of it.
Continue raking until you hear all of the wafers fall against the cylinder. If the lock is a double wafer lock, repeat this process on the bottom as well.
If you cannot release every wafer by raking, use the lock pick to push each wafer out of the cylinder individually, and let it fall back into the cylinder. Do this by placing the tip of the pick on the ceiling of the lock and feeling for individual pins. They should fall against the outside of the cylinder.
Once every wafer is released, turn the lock using the tension wrench. It should open freely and easily.
Some Sentry safes use more advanced locking mechanisms. Consult the manufacturer if you are unsure about what type of lock your safe uses.
Never use this method to open someone else's safe without permission. Theft is a very serious crime.