The invention relates to a method for manufacturing hollow profiles, having the following method steps: providing an initial hollow profile which in an insertion wall and optionally in at least one intermediate wall displays an insertion opening, providing a support element which displays a bolt element, an engagement element, and support walls which are disposed between the bolt element and longitudinal flanks, passing through the support element through the insertion opening until the support walls are positioned in the initial hollow profile, engaging a tool on the engagement element, rotating the support element by means of the tool until regions of the longitudinal flanks touch inner walls of the initial hollow profile, connecting the regions of the longitudinal flanks to the initial hollow profile via the inner walls.