Final answer:
Using a length of pipe over the handle of a wrench increases the torque and leverage, making it easier to remove tight bolts. However, caution is required as excessive force can break the bolt.
Step-by-step explanation:
When mechanics use a length of pipe over the handle of a wrench to remove a tight bolt, it helps increase the torque or turning force applied to the bolt. By adding the pipe, the mechanic can exert more force and leverage to loosen the bolt, making it easier to remove. However, this technique can also be hazardous because the increased torque can break the bolt if excessive force is applied.