The invention relates to an embodiment of a very long post which consists in dividing it into two parts (foot-extension and post body) which results in elements having a weight and length allowing the use of injection moulding of plastic, hence the mass production of very durable equipment. The foot-extension comprises fins a maintaining the assembly vertical, ribbings c providing stiffness whilst saving on material, a socket d receiving the post body p, a reinforcing ring b preventing the deterioration of the socket and being possibly used as a base for a piece facilitating the driving-in of the foot-extension by machine (which is made possible by the reasonable length of the foot-extension). The assembly of the post body onto the foot-extension (which may have been placed into position well beforehand) is carried out by gravity, is instantaneous and allows a complete interchangeability, which is also instantaneous, of bodies of varying lengths. The device thus described is particularly useful in the field of fences and of plant-training elements of great height. <IMAGE>
