One of the very first things people did with lasers after they were invented was to use their beam as a reference for construction. Put a laser on a transit mount and you have a great way to keep things level or in a line. A late '60s era version of such a thing is this Spectra-Physics model 120T mounted on their model LT-3 laser transit mount. Included are pics from the book "Applications of the Laser" by Leon Goldman (1973) with the parts labeled and showing it in operation in a tunnel.
Here's a pic of their model LT-2, from "Lasers and their Applications" by Beesley (1972).