The ones sold at Home Centers are called landscaping blocks. They're fairly heavy - perhaps 20 lbs apiece. Measure about 12 x 6 x 4" thick.

If you can work with the weight, you need to dig a trench about 6" deep. Place a couple inches of limestone screenings on the bottom, using this to create a level base. The first row of block will be at or below ground level. Use a level adding or removing screenings to make this row level. The remaining rows are simply stacked atop like a brick wall. You can use adhesive to secure the blocks to one another if you wish.

I've done it and it is work. If you take your time though and do a little at a time you'll be fine. Good luck.

Thank you. I don't think I will be doing that. Didn't realize they were that heavy. I think I was thinking of something 1/2 that size.

The smaller ones aren't heavy enough to remain in place and retain soil. There use to be one with a pre-drilled hole for driving a pipe through. When you're at a nursery or home center, take a look at what is available. Could be something I'm not familiar with.