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.
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
TV bracket Kromax DIX-18 black
52 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
β Stainless Steel L-Square, Size 3-Inch x 4-Inch, Zona 37-434
8 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
Laser level DEKO LL57 SET2 with tripod
19 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