Apparatus extensible and shortenable to a mast or support, characterized in that this comprises a number of frame- or plate-shaped.segments, each having a left side edge, a right side edge, a bottom edge and an upper edge, whereby the bottom and upper edge [4, 5] are provided with connecting means for the formation of a releasable or fixed vertical link of the upper edge of the one segment to the bottom edge of the other segment, such that a number of at least two, three, respectively four, five or more segments is or can be formed into a chain, whereby the side edges [2,3] of the segments [1[] are provided with connecting means for the formation of a releasable horizontal link of the left side edge of the one segment to the right side edge of the other segment, such, that a number of at least three, respectively four, five or more segments can be put together into a tube having in cross-section a triangular, respectively quadrangular, pentagonal or polygonal form, whereby means are provided by which the horizontal link between the segments can be brought about and can be undone, which means are formed by a drive station, provided with a vertically mounted hollow lead-through for the segments, which hollow lead-through comprises: a middle part in a form becoming narrower from below to above, an upper part for the upwards feeding out and downwards feeding in of segments that have been linked into a tube, and a lower part that runs out downwards radially in at least three guides [24, 25, 26] or more guides, whereby each guide is intended to take up and guide one chain of segments, whereby drive means are provided for the moving from the guides upwards towards the middle and upper part [20, 21], or for the moving from the upper and middle part downwards back towards the guides, of the chains of segments, whereby the internal form of the middle part is adapted to the shape of the segments, such that the chains of segments in the course of their movement upwards are moved or forced with their side edges towards each other and the connecting means for the formation of the releasable horizontal link of the left side edge of the one segment connect to the connecting means for the formation of the releasable horizontal link on the right side edge of the other segment characterised in that the chains are positioned relative to each other in the guides in such a way, that on the coming about of the horizontal link the segments are linked to each other a portion of the height shifted. a middle part in a form becoming narrower from below to above, an upper part for the upwards feeding out and downwards feeding in of segments that have been linked into a tube, and a lower part that runs out downwards radially in at least three guides [24, 25, 26] or more guides, whereby each guide is intended to take up and guide one chain of segments, whereby drive means are provided for the moving from the guides upwards towards the middle and upper part [20, 21], or for the moving from the upper and middle part downwards back towards the guides, of the chains of segments, whereby the internal form of the middle part is adapted to the shape of the segments, such that the chains of segments in the course of their movement upwards are moved or forced with their side edges towards each other and the connecting means for the formation of the releasable horizontal link of the left side edge of the one segment connect to the connecting means for the formation of the releasable horizontal link on the right side edge of the other segment characterised in that the chains are positioned relative to each other in the guides in such a way, that on the coming about of the horizontal link the segments are linked to each other a portion of the height shifted.