Right Angle
Right angle is also olden basic tool made of wood,mild steel sheet,stainless steel with cast iron handle used for various engineering works.actualay it used every where in engineering field.especialy for inner or outer corner checking .it made on right angle (90°)triangle rule that at every step of angle is as at right position. by measurement a famous rule called 3,4,5 here 3 is perpendicular 4 is base and 5 is hyputios.in our field if any surveyor does not know about right angle