Abstract: This convertible structural element comprises two link chains (1, 2) which, after assembly, are capable together of assuming the form of a rigid beam. The links (3, 4) of the two chains are provided with antagonistic bearing points (10, 11), the first bearing point (10) of a link of rank n of each chain interacting with a second bearing point (11) of a link of rank n-1 in order to trap fastening elements which the pins (7, 8) of the links of the other chain form, when the element is made rigid. At least some links of at least one of the chains of the structural element exhibit a row of teeth (13) which, together with the teeth of the neighbouring links in the direction of the length of the element, form a continuous toothing extending laterally over the entire length of the element.