pins 19 and 21 will enable the jib 1 to be unfurled that is to say will enable the second jib element 3 to be brought back into the direct continuation of the first jib element 2 during these manoeuvres the operator stations himself in a gondola of the jib crab 4 from where he can without danger perform the operations of pinning and unpinning the two pins 19 and 21 fig7 and 8 illustrate one use of a tower crane provided with a jib 1 as previously described the crane here being depicted complete with its base chassis 22 and its mast 23 at the top of which the jib 1 is mounted the application in question is the construction of a cooling tower 24 of a thermal or nuclear electricity power station the mast 23 of the crane standing along the vertical axis of the cooling tower 24 under construction as fig7 shows when the construction of the cooling tower 24 is over this tower 24 obstructs a dismantling of the crane simply by shortening the mast 23 accompanied by a lowering of the jib 1 by contrast as illustrated by fig8 furling the jib 1 by folding the second jib element 3 on top of the first jib element 2 as described previously u201c shortens u201d the jib 1 allowing it to be.