THE PROBLEM:

Landscape blocks step back 2 inches
on every course. When using corner blocks, they also step in 2 inches to adjust for the wall running in the other direction. If only one corner block is used, this offset is unnoticeable and easy to deal with. When using two corners, as shown above, the wall gets squeezed 4 inches on each course.

THE SOLUTION:

Key blocks are 4 inches shorter than the standard block - 44 inches versus 48. use one additional key block for each successive course feeling the squeeze. For example, on the first course no key blocks are required. The second course needs one key block, the third course needs two, the fourth course needs three, and so on. At 12 courses the wall is being squeezed 48 inches and does not require a key block - simply start the pattern over again.