How to get 90 degree angle on ground?

Answer 1

Make a 3 4 5 triangle on the ground.You need 3 tape measures ( 25 ft long ) or 1 string 15 ft long and another 20 ft long and 1 25 ft tape measure. Measure a 15 ft line one direction and a 20 feet line as close to perpendicular (90 degrees) to the 15 ft line. Use the 25 ft tape measure to make sure the end points of the 15 and 20 ft lines are exactly 25 ft apart. You don't have to measure 15,20, and 25, but I suggest making the lines as long as possible to make sure the 90 degree angle is accurate as possible.