Intergluteal Cleft is the technical term for butt crack. It is located in the two inches just below where the buttocks connects with the lower back. Many times the Intergluteal Cleft can be exposed by people bending over while wearing low cut, miss fitting jeans.
While bending over to pick up his tools, the plumber exposed his intergluteal cleft. He really should look in to getting that waxed.