A pendulum, a sensor and one tap.
Plumb One is simple on purpose. Here is what happens between holding it to the wall and seeing a line you can trust.
Stick
The magnet back grips steel studs and beams. On drywall, a pin tab goes in first and Plumb hangs from it. On a tripod, the ¼″-20 thread does the job.
Aim
The laser module hangs from a damped pendulum. Gravity does the leveling; a sensor double-checks and the ring colour tells you the result.
Mark
Draw along the line. One tap saves the angle to the phone app so the next wall starts from the same height.
Settles in about 0.4 seconds.
Knock it and the pendulum swings, but heavy damping pulls it back quickly without overshooting much. The curve shows the beam error after a 4° knock in the simulator model.
Natural frequency 14 rad/s, damping ratio 0.7. A 2% settling time of 4 ÷ (ζ·ωn) comes to 408 ms. Past ±5° the pendulum reaches its mechanical stop and the beam turns coral.
Three ways to hold a line.
Pick the one that fits the wall, not the other way round.
Magnet back
For steel studs, door frames and beams. Soft rubber face, no marks.
Pin tab
For drywall and plaster. A fine pin leaves a hole smaller than a sewing needle.
Tripod thread
For floors and long runs. Standard ¼″-20, so any camera tripod works.
A tool, not a toy.
Concept notes for a visible-laser product.
Do not stare into the beam
A real Class 2 laser is safe for brief accidental exposure. Never point it at eyes.
Not a surveying instrument
Fine for hanging, shelving and tile. Use certified tools where certification is required.
Check it yourself
Flip it end for end on a wall: if the two marks differ, you know the error. Good practice with any level.