Concrete engraving is the process of cutting or scoring lines in the surface of concrete to create patterns and designs. You can engrave concrete to give it the appearance of tile, brick, stone, etc. It's also used to keep a separation between colors if you're painting or staining the concrete.
This patio was one of my first engraving jobs. Not bad and it didn't take too long either. Unless you have the sophisicated tools, it's impossible to make perfectly straight lines, but that's okay. Minor squiggles aren't all that noticeable.
Concrete engraving can be simple or extremely difficult depending on the detail of the design. It can also be very expensive because most engraving requires skilled tradesmen for highly detailed patterns and designs. So for the do-it-yourselfer, I recommend keeping it simple.
The first step is drawing the pattern on the surface with a pencil. Once you're satisfied with the pattern, trace over the penciled lines with a marker because saws and grinders will blow the pencil marks away and erase your lines.
For thin lines, use a circular saw with a 7 inch diamond blade to score long straight lines using a straight edge such as a 2x4 board as a guide. Make sure you set the blade depth to about 1/16 inch. An angle grinder with a 4 inch blade works well for shorter lines.
A masonry cut-off blade with an 1/8 inch cut also works well for circular saws and angle grinders. It makes wider lines than a diamond blade and it's easier for scoring curves.
If you want wider scores, use a 4 inch masonry grinding blade with a 1/4 inch cut on an angle grinder. This works really well if you're trying to create the appearance of grout lines or you just want the lines to be more visible.
Always wear safety glasses when cutting and scoring concrete!