a single cardboard sheet folded about a longitudinal reinforcing member the invention further provides frames preferably human powered vehicle frames constructed from structures of the invention as well as methods for producing structures of the invention application_number US 201615068523 A description in the following description although at times particular mention of a specific figure will be made reference is mostly to the figures in their entirety reference is first made in particular to fig1 and 2 showing a bicycle 100 having a steering arrangement 110 a frame 102 a seat 150 wheels 160 and a crank assembly 170 the frame 102 comprises a front frame part 120 and two rear frame parts 140 the two being mirror images of one another each of the frame parts is made substantially of cardboard as will also be further explained below as best seen in fig3 a to 3e the front frame part 120 comprises two integral elongated elements l 1 and l 2 and a support element 126 which is also integrally formed with the two elongated elements l 1 l 2 end portions 127 l 1 and 127 l 2 of the longitudinal elements l 1 and l 2 respectively serve as the site for association with corresponding elements 147 l 1 u2032 and 147 l 2 u2032 of the rear frame part 140 the bicycle seat 150 and the crank assembly 170 as can be seen the end portion 127 l 2.