Underaged Pilot,
A pull test is a safety procedure intended to establish that your handle, lines, and bellcrank mount are strong enough to handle the flight loads. At a contest the pull test will be done with a scale, usually a modified fishing scale, hooked to the handle. One person holds the scale and the pilot holds his model and pulls on it up to the specified force. Most of us who have been around a while have had,or seen, a control system break during this test. The AMA rule book specifies the amount of pull for different competition events and different weights of models. Pull tests should be done with a smooth pull. Jerking or "twanging" the lines can cause a failure. BTW, rule books are free from AMA, just ask. Even if you don't have a scale, a good pull of about twice what you expect the model to do can make you feel better about the security of your system.

Saftey thongs are straps, mine are heavy duty boot laces, that connect the handle to your wrist. They prevent a flyaway if you let go of the handle.