You need to have two people for this particular drill. One person holds the pads (preferably muay thai pads or focus mitts) as the other one blocks. The pad holder simulates different strikes as punching while the other partner blocks. There are 5 basics blocks I’ll talk about for this drill, probably the most used. They are the basic forms of blocking, building the proper foundation for more advanced training.
You have the side block, where you block with your outside forearm. This block is used for blocking jabs, crosses, any even high kicks, though in some cases, I’d prefer to move out of the way.

Practice this drill:

Pad Holder: shoot your arm out with the pad at the blocker.
Blocker: Bring your arm up, the outside of your forearm should hit the pad.
Practice this drill to failure.