Almost everyone has lost or misplaced an important key. But that doesn't mean you have to spend money on a locksmith. You can open a locked door without a key and without causing damage.
Place the short end of the tension wrench into the lock as far as it will go. Turn it in the direction that you normally turn your key to open the door.
Stick your pick into the lock while keeping your tension wrench turned in the same direction. Push the pick in as far as it will go and run it across the top of the pins back and forth.
Rake the pick up and down and back and forth. This is the part where you will need to have the most patience. You need to push the pins in the correct configuration that mimics the ridges in your keys; trial and error is the best way. You will eventually hit the pins with your pick in the right manner, and as long as you've kept your tension wrench turned, the lock will also turn and the door will unlock.