Technician a says that when using the brake pre-adjustment gauge, you should set the gauge to the drum diameter and lock it in place. technician b says that you should place the pre-adjustment gauge over the center of the brake shoes during the adjustment process. who is correct?

Both technician A and is correct.

Explanation:

Because first one says that the user can be set the diameter of the drum gauge and then, it lock in place when the brake for the following pre-adjustment gauge. After the first one, the second one says that the user can place that following pre-adjustment gauge in the middle of the shoe brake at that time when they processing the adjustment brake. So, both are saying true about the pre-adjustment gauge process.

(because i need 20 chars)