In this paper we develop the lower and upper solutions method for the fourth-order boundary value problem of the form y (4) (x) + (k1 + k2)y ′′ (x) + k1k2y(x) = f (x, y(x)), x ∈ (0, 1), y(0) = y ′ (1) = y ′′ (0) = y ′′′ (1) = 0, which models a statically elastic beam with one of its ends simply supported and the other end clamped by sliding clamps, where k1 < k2 < 0 are the real constants and f : [0, 1] × R → R is a continuous function. The proof of the main result is based on the Schauder fixed point theorem.