This occurs in any case where you have a wall on one side of your pattern, and a 1 directly after the wall.

The first 1 only has two squares touching it, and it shares those two squares with the second 1:

Since there is a bomb in either the first or second square, there cannot be one in the third square, because they are touching the second 1. So, you can clear the third square:

There are other situations where this pattern can be applied, where certain patterns mimic a wall:

Of course, this can also be applied to the top, right, and bottom walls as well.