How to calibrate a laser level on a construction site; do these two steps before laying out lines.

On small job sites, everyone relies heavily on a laser level, but very few people check the instrument first. We previously encountered a level that hadn't been calibrated after being dropped, and the baseline for an entire row of cabinets was off by nearly 1/4 inch. I now perform two checks before laying out lines. First, find a wall to perform a two-way test: place the instrument a few meters…