"z" wrote:

-snip-
Home Depot had some little pads of handouts about building retaining
walls. I think the product associated with them was some big screws for
holding things together.

Timberlock? I love those things-- They are about 50cents apiece,
but I keep a box of 6 & 8 inchers around to tie those 3x5 landscape
timbers together. I drive them with a 1/2 inch drill. Usually I
retrieve them when I[or my chief architect, aka wife] change my
landscape plans. [frequently] They outlast the cheap timbers I'm
holding together.

Googling for Timberlock & landscaping might bring up some ideas.

Jim