straight line 19 that passes through the center of and is perpendicular to the axis 13 this result is accomplished by forming the web 9 as a regular trapezoid with sides diverging at 2 5 u00b0 from the centerline 13 for a total divergence at the intersection of the arc 12 and the upper edges 21 and 22 of triangular sections 4 and 7 respectively of 5 u00b0 the angular values given herein are for a particular configuration of printer and are not intended to be limiting the angles are of necessity tailored to specific structures each linear intersection of triangular and rectangular sections is defined by a fold line 23 referring now specifically to fig2 and 3 triangular sections 4 6 7 and 8 have been folded along fold lines 23 so as to be positioned at right angles to rectangular sections 2 and 3 whereby to define two c shaped members the top members 4 and 7 of the 34 c 34 as viewed in fig2 taper down as they approach the web 9 and it will be readily noted in fig3 that the bottom and top surfaces of the folded structure slope downward due to the 5 u00b0 divergence of the web 9 also it is apparent from fig3 that the distance between the bottom and top surfaces of the left member are equal to the distance between the inner surfaces of triangular members 7 and 8 referring now specifically to fig4 and 6 of.