"RubberBiker" wrote in message
...
It's noticeable that very few pro tools have laser guides, seems more
common amongst diy-market CS's and mitre saws.

However an exception is a high-end SCMS from festool:

http://www.axminster.co.uk/product-F...Saw-718884.htm

So it might be that a really good solution to laser guides is as yet
too expensive for wider adoption.

They work if they are adjustable.
You need it to line up with the edge you are using or have two one on each
edge.
I don't use one, the length is either not that critical or you push the end
up against the stop you have set accurately.