The test sit and reach is a common measure of flexibility, and specifically measures the flexibility of the muscles of the back and lower hamstring.
This test is to sit on the floor with your legs stretched forward. Shoes should be removed. The soles of the feet are placed flat against the box. Both knees must be closed and pressed downward - tester can help by holding down. With the Palms down and hands at the top of one to the other or next to each other, that the subject reaches forward to along measurement line as far as possible. Make sure that hands are kept at the same level, not a broader reach forward than the other.
After a little practice reaches, the subject extends and holding that position for one to two seconds, while the distance is recorded. Make sure that there is no sudden movements.