1.new truck, characterized in that parallel to the perpendicular appendages of the trucks and that constitute the two points of support of the truck on the ground when it is in rest position, there are two more appendages also perpendicular and parallel to those before mentioned, having at the end of these four appendices located two to two in the respective side arms of the truck, a perpendicular notch in which is inserted in each of them a rotary wheel with throat in its trowel in which is housed a belt, trapezoidal, endless, that goes from the wheel of an appendix to the other parallel appendage of the same arm being the tension of the belt regulated, at will, existing means of tensioning in the own wheels which trapezoidal belts has as mission the that when the truck is loaded when descending the steps of a stairway, act as an endless belt of displacement this facilitates the descent or ascent of the truck, depending on how it is inclined, as the weight of the load is mainly affected by trapezoidal belts that are tensioned and moveable in endless traction caused by the rubbing of the edge of the steps. The ladder, and support against them, the weight that moves and the direction of the truck. 2.new truck, according to the previous claim, in which on one of the arms there is on its internal face an automatic winding drum, by virtue of an internal spring, of the end of an endless band, eventual, flexible that from the the arm of the trolley in which the drum is located covers the other arm thereof and rerolls to the drum itself, said band having a temporary solution when releasing one of the two opposite ends thereof when the arm is eventually removed from a fork. Bridge connecting one end loop to the other end of the endless band, this arrangement permitting the attainment of a safety belt for rapid and progressive securing of the load arranged on the truck; with the automatic rotation of the drum by pulling the spring and pulling the spring and simultaneously pulling the two ends of the flexible band to it coiled. 3.new truck, according to the previous claims in which there is a pin for fixing the flange with holes of the rotation of the winding drum on itself regulated, the band without end eventual. 4.new truck, according to the previous claims, in which each arm of the tube truck of rectangular or square section presents on the side facing the other arm and at the height close to the other arm and at the height close to the birth of the final curve of each arm, an orifice in which a perpendicular appendage of the inner side of an additional arm is inserted, which also has two rigid flanges, laminar, perpendicular, each angled at a slightly straight dihedral angle placed one behind the other and opposite each other and between them figure located the perpendicular appendix of each additional arm that is juxtaposed to the side of the side with hole of his main arm of the truck and with bent through the insertion of the additional arm into the hole of the main arm that is located interspersed in the space determined by the separation of one and the other flange, is printed on the arm additional a turn until it is aligned to the main arm and meanwhile, automatically, in the same action of rotation of each flange is coupled to the main arm to embrace the arm by two opposed points to be positioned one and another rigid flange facing each other with the main arm interleaved, and also having a pin fixing the working position of the additional arms. 5.new truck, according to the previous claims, in which in addition to the support of the fork itself of the trucks there is another, folding, which is formed by two elbow blades joined together and their rear ends wound on itself constituting rotating clamp on a cylindrical crosspiece in which said crosspiece between the main arm and arm of the truck is grasped and pivoted. 6.new truck. (Machine-translation by Google Translate, not legally binding)