Hₓ(s) = diag(s, 1, 1) stretches space along x by the factor s and leaves the plane x = 0 fixed. Its determinant is s, the signed volume of the unit cube's image. At s = 0 the cube is crushed flat onto the plane; at s = −1 the map is the reflection I − 2nnᵀ, with H² = I and