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.
Empire Level E250M: 12-Inch Heavy Duty Professional Combination Square with Etched π Stainless Steel Blade, Metric Graduations and True Blue Vial - Accurate Measurements Guaranteed
8 Review
β Stainless Steel L-Square, Size 3-Inch x 4-Inch, Zona 37-434
8 Review
π Johnson Level and Tool 400EM-S 12-Inch Heavy Duty Metal Combination Square for Professionals, with Inch/Metric Measurements, Silver - 1 Square
8 Review
Kapro - 353 Professional Ledge-It Try & Mitre Square - For Leveling And Measuring - Features Stainless Steel Blade, Retractable Ledge, And Etched Ruler Markings - 12 Inch
23 Review
21 Inch Heat Resistant Stove Gap Covers - Kitchen Counter Sealing Spills Protection (2 Pack, Semi-Clear)
21 Review
Laser Level, 98Ft Green Self-Leveling Laser Line With Magnetic Base, With Adjustable Lightness Line Cross Laser Level For Picture Hanging - KAIWEETS T03
18 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
ICEPURE 2PACK Replacement for GE MWFINT, 197D6321P006, WFC1201, GSH25JSDDSS, PSHS6PGZBESS, SGF-G9, RWF1060 Refrigerator Water Filter - Efficient Filtering Solution for Your Fridge
22 Review