I keep a set of these tools in my tool box and use them regularly when setting up lathes or mills. The four different sizes are very handy depending on what kind of interference I want to set up. As others have said, they're not entirely accurate, but very useful in situations where disabling them isn't a big deal.
Laser level DEKO LL57 SET2 with tripod
19 Review
Precision Laser Level: Firecore 2X360 Self-Leveling Green Beam Tool With Pulse Mode And Rechargeable Battery For Accurate Alignment And Versatile Use
22 Review
21 Inch Heat Resistant Stove Gap Covers - Kitchen Counter Sealing Spills Protection (2 Pack, Semi-Clear)
21 Review
π CAMWAY 6 Inch Digital Caliper with LCD Display, Electronic Vernier Caliper, 150mm Stainless Steel Feeler Gauge, Plastic Digital Caliper Set for Zero Setting Inside/Outside Diameter, Depth, and Step Measurement Tool
3 Review