a framework adapted for mounting on a vertically oriented planar substrate;

at least one plurality of rigid retaining rings, arranged on said framework in a fixed predetermined configuration, spaced apart from each other, and adapted to extend orthogonally with respect to said framework; and

at least one resilient cord having a predetermined untensioned length, threaded through a respective plurality of the rigid retaining rings, a segment of said resilient cord being adapted to resiliently support engagement with a body part of a stretching person,

wherein each plurality of retaining rings includes at least 6 rings, arranged with 2 central rings vertically aligned with each other, 2 left rings arranged on a left side of said framework and 2 right rings arranged on a right side of said framework, said central rings being vertically offset with respect to said left and right rings, thereby causing segments of said resilient cord which pass from said central rings to said left or right rings to assume respective slanted paths.