The goal in picking a deadbolt is to arrange six to eight small pins inside the lock (called tumblers) to the appropriate height so that they are no longer obstructing the lock cylinder from turning. Once the pins are out of the way and the cylinder can rotate freely, the deadbolt can be slid easily in and out as the cylinder turns. This needs to be re-created with a lock pick.

The Tools

You need two pieces to pick a deadbolt successfully. One is a torque tool which is a skinny flat piece of metal. It has a 90-degree bend at the end of it that will insert into the lock cylinder. The other is the actual pick which is another flat piece of metal that has a triangular bump at the end of it for positioning the lock pins. The pins are held in place inside the lock by small springs. When a key is inserted in the keyhole, the grooves in the key raise each pin to the appropriate height to allow the cylinder to turn. These tools can be purchased or you can make your own. Street sweeper bristle works well because it is very thin and very durable. The pick needs to be able to slide in and out of the lock freely so it can work the pins smoothly.

Picking the Lock

You need to apply constant torque pressure by sliding the torque tool into the lock and twisting it as if you were turning a key. Rotate it as far as it will go and then keep slight pressure on it to hold it in that position so it can keep the lower pins in the up position. While keeping pressure on the torque tool, insert the pick and start manipulating the pins by jiggling the pick up and down and moving it back and forth. As each pin hits its sheer line, the cylinder will rotate a tiny amount thanks to the torque tool and this will hold that pin in place. Once all the pins are in position, the cylinder will rotate all the way open. Another easy way to do this is to just slide the pick in and out while keeping pressure on the torque tool. The vibration of the pick rubbing across the pins as it goes in and out of the lock will gradually slide each pin into its position for the cylinder to turn. Patience is key as this can take some time if you've never done it before and will become easier with practice.

Source:

Irvine Underground: How to Pick a Deadbolt

YouTube: How to Pick a Deadbolt Lock

GregMiller.net: Greg Miller's Guide to Lock Picking for Beginners