This guy lets you check ALL your other squares and discard the ones that aren't VERY close together. Yes, it's expensive, but it's the benchmark for 90 degrees in your shop.
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
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
π² Johnson RAS-1B Johnny Square: Professional Aluminum Rafter Square, 7'', Silver - Top Quality with 1 Square
8 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
High-Quality Beaquicy Replacement Dryer Lint Filter And Cover Housing Set For Kenmore And LG Dryers (ADQ56656401 And MCK49049101 Models)
19 Review
Laser level DEKO LL57 SET2 with tripod
19 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