3-4-5 method is commonly used for setting out the right angle by using the tape which gives pretty accurate right angle and is widely used in day to day practice.
Person 1: holds the zero mark & 12m mark of tape
Person 2: holds the 3 meter mark of the tape
Person 3: holds the 8 meter mark of the tape
When all the sides are stretched, a triangle is formed and the angle near position or person1 is a right angle.
We can either use: 3-4-5 m
Or other multiplies too, depending upon the situation, say