The braking system includes your discs, pads, calipers, brake lines and the handbrake. When you need your brakes repaired, particularly if they have failed an MOT, we need to identify which part of the braking system has failed. For example, if the discs needs repair, (you might be able to see the disc and the brake pads through the gaps in your wheel), we will check that the face of the large round discs are smooth and there is enough friction material left on the brake pads. The legal minimum level for a brake pad is 1.5mm. The less pad you have, the more ineffective the brakes will be. Less friction material means less heat dissipation, which in turn means your brakes could overheat. The pads are located either side of the brake disc.
Your handbrake is also part of the braking system. Check out this old blog post from our archives, which helps you to identify if your handbrake needs an adjustment: How to Know if Your Handbrake Needs Adjustment?