We install quality, heavy-grade deadbolts. Only heavy-grade deadbolts will stand the test of time while also securing the entryway. Lower grade deadbolts, most commonly found at hardware stores are made with white metal and/or plastic internal parts. These deadbolts not only malfunction but they aren't nearly as secure as a heavier grade deadbolt. The cost difference between this lower grade and heavier grade hardware is usually minimal. 

Doors that are equipped with only a knob lock are vulnerable to being jimmy'd or "credit-carded" open. It only takes seconds and the door can be opened using only a credit card or a small screwdriver. Installing a deadbolt would require the person to not only have the knowledge on how to disable the lock but also the time.