This paper deals with the existence of solution for the fully fourth-order boundary value problem u (4) (x) = f (x, u(x), u (x), u (1), u (x)), x ∈ [0, 1], u(0) = u (0) = u (1) = u (1) = 0, which models a statically elastic beam fixed at the left and freed at the right, and it is called cantilever beam in mechanics, where f : [0, 1] × R 4 → R is continuous. Some inequality conditions on f guaranteeing the existence and uniqueness of solutions are presented. The inequality conditions allow f (x, y 0 , y 1 , y 2 , y 3) to grow superlinearly on y 0 , y 1 , y 2 , and y 3 .