A box erecting machine that can readily be set up to assemble boxes of different sizes contains pointers and scales permitting the vertical and horizontal adjustment of the box magazine, the centering of the flap folding structures, and the vertical adjustment of the box hold down plates to be readily set according to the dimensions of the box to be assembled. The vertical adjustment of the box magazine, the horizontal adjustment of the box magazine, and the centering of the flap closure apparatus are adjusted until the corresponding pointer and scale of those structures indicate the width measurement taken directly from the box. The hold down plate assembly is adjusted until the corresponding pointer and scale indicate the height of the box as measured directly therefrom. Horizontal adjustment of box magazine width and horizontal adjustment of an adjustable guide rail are performed against an actual box placed in those structures. Alternatively, the scales corresponding to the critical parameters can be pre-marked with graduations corresponding with the boxes typically assembled by the user.