I assume you are aligning your chain, sprockets and rear wheel with this method. That is very clever and elegant. Way to go.
I saw laser chain alignment tools, but dang, they cost a lot up to almost $200. So I thought I'd use a regular laser level from Home Depot. (I cheered when the Lowe's opened around here, I have terrible luck with the Depot).
I bought the first laser level that I saw, I'm sure there are better units. But $39 and almost no time invested sounded good to me. I want the sprockets and chain straight, straight, straight, and I was frustrated with the ways I'd tried to align everything.
I stick this laser level
on an 18" or so 2x4 standing on it's end behind the rear wheel so it can look down the rear sprocket along the chain to the front sprocket. I try to get the beam to draw a red line right in the middle of the chain links the entire length of the chain and all the way down the rear sprocket. I use the leveler bubbles to make sure the bike is not ever so slightly canted to one side or the other on the center stand.
The biggest difficulty is my setup isn't very elegant. Lining up the blocks of wood (I use two blocks, one flat, one stading up) is kind of awkward. I keep telling myself I'll make a stand for the laser but awkward or not, if I can line up that beam along the chain with a bit of fidgiting, about 30-45 seconds per each line up of the laser, that baby is straight and I'm happy.
The way I do all this is awkward because I dont' have a good stand for the laser. But it is all worth it when I see everything very straight. I'll have an elegant method when I get a good stand figured out. Right now I'm fine with awkward.