In the present paper, by using the mixed monotone operator method we prove the existence and uniqueness of positive solution to the following cantilever-type boundary value problem u(4)(t)=f(t,u(t),u(αt))+g(t,u(t)),0<t<1,α∈(0,1),u(0)=u′(0)=u′′(1)=u′′′(1)=0.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\begin{aligned} \\displaystyle \\left\\{ \\begin{array}{l} u^{(4)}(t)=f(t,u(t),u(\\alpha t))+g(t,u(t)),\\quad 0<t<1, \\quad \\alpha \\in (0,1),\\\\ u(0)=u'(0)=u''(1)=u'''(1)=0. \\end{array}\\right. \\end{aligned}$$\\end{document}Moreover, in order to illustrate the results we present an example.