POSTCONNECTION MEANS FORLOADVEHICLES, ANDMANUFACTURINGMETHOD The present invention generally relates to a post connection means for a load vehicle, and to a method of manufacturing such post connection means, and the invention is more particularly directed to a post connection means which is stationary mounted adjacent the sides of a load platform of a vehicle, and which is arranged for quickly and simply, but at the same time safely, securing a side post onto the vehicle, and which post can also quickly and simply be released, so that the load platform can be used for other purposes than for transportation of elongated objects like timber etc., and which need very stable side supports. A post connection means is priorly known which is arranged to be introduced through a bore which is provided in the supporting frame of the load platform of a motor vehicle, and to be fixed connected in said bore by welding or in another way, and which comprises a sleeve having a length of 2-4 times the diameter of a circular load post, for instance a couple of decimetres, and which is formed with a through slot extending from the upper edge of the sleeve as far as to a place close to the bottom of the sleeve, and which at said lower end is ended by a bayonet sleeve portion of a type known per se having an inclined bottom edge and a parallelly of nearly parallelly thereto formed upper edge. A load post is adapted to be introduced and to be secured in said sleeve in that a projection pin at the lower part of the post is moved down in the through slot of the sleeve and is secured in the bayonet sleeve by being rotated when in its fully moved down position. For keeping the sleeve together and preventing a deflection of the sleeve at the vertical through slot, which may be caused by the large side forces that the post can be subjected to, the sleeve is formed with a rib at the outside thereof, which rib is welded to the post on each side of the slot. A post connection means of the said type is shown in figure 1 of the drawings. The interconnecting rib has substantially the same thickness as that of the sleeve, and hence it projects a distance out of the periphery of the sleeve. The manufacture of the rib and the welding thereof to the sleeve is time consuming and involves costs. The existence of the projecting rib also involves problems when providing the bore therefore in the load platform in that also said introduction bore must be formed with a recess corresponding to the projecting rib of the post. The placing of the said bore recess also restricts the possibility of placing the post socket in any optionally rotated position on the load platform. The object of the invention therefore is to solve the problem of providing a post connection means without any projection parts, and in which the guide groove for the projecting pin of the post is formed like a slot which is provided inside the sleeve bore and which does not extend all the way through the thickness of the sleeve material. The invention also relates to a method of manufacturing a post connection means of the said type. According to the invention the post is formed with a vertical or nearly vertical guide groove for the projecting pin of the post, which guide groove is provided from the interior of the sleeve material, and which does thus not extend through the sleeve wall material, and said vertical or nearly vertical guide groove is, at the lower end thereof, extended into a bayonet groove which, for manufacturing reasons, extends through the sleeve wall material, but which may eventually be formed non-through, like the vertical guide groove, and which, as known in the art, is formed with an inclined bayonet locking groove extending peripherally out of the vertical guide groove. The vertical guide groove may have any cross section shape, like rectangular or bow formed. In a preferred embodiment of the invention said vertical guide groove is provided by being drilled or cutter milled so as to form an arc from the interior side of the sleeve, which groove is connected to the bayonet groove, which can be provided before or after the vertical guide groove is provided. In a first embodiment of the invention said vertical guide groove is drilled or cut out so as to provide a substantially semi-circular or circular segment groove, see figure 6. Alternatively two, or eventually several circular segments may be drilled or cut out adjacent each other, so that said two or more circle segments in common form the vertical guide groove, see figure 7. If desired the top between the two co-operating circle segments can be ground or cut away, so that the bottom of the guide groove is formed substantially flat, see figure 8. Now the invention will be described more in detail with reference to the embodiments thereof shown in the drawings. In figure 1 there is shown a perspective view of a post sleeve according to prior art. In figure 2 is correspondingly shown a post sleeve according to the invention. Figure 4 shows a first phase of the introduction of a post into the connection sleeve, and figure 5 shows the post in its fully mounted position in the connection sleeve. Figures 6, 7, 8 and 9 disclose, as seen from above, four different shapes of the vertical guide groove of the sleeve. The known post connection sleeve shown in figure 1 comprises a sleeve 1 having a axial through central bore 2 for introducing of a post 3, which is shown in figure 3. The sleeve 1 is formed with a vertical guide groove 4 for a pin 5 of the post 3. The guide groove 4 is provided entirely through the material of the sleeve 1 , and at the bottom end thereof it is ended by a bayonet groove 6 which, as usual, extends sideways of the vertical groove 4, that is in the peripheral direction of the sleeve. In the known embodiment the bayonet groove 6 extends entirely through the material of the sleeve. At the exterior side the sleeve is formed with a rib 7 which is wider than the guide groove 4 and which overlaps same at the exterior side of the sleeve 1 and is welded to same by vertically extending weld joints 8. As mentioned above the said known apparatus involves some disadvantages which have been eliminated by the apparatus shown in figures 2-9. In said figures there is shown a sleeve 10 having an inner axial circular cylindrical bore 12 adapted to the introductory part 3a of a post 3 which is formed with a radially extending guide and lock pin 5. Above the introductory part 3a the post is formed with coarser post part 3b which both is formed as a support surface against the upper edge of the sleeve 10, and also provides a strengthening post part for supporting the load on the vehicle. For guiding the post 3 while it is being introduced into the sleeve 10 said sleeve is formed with an inner guide groove 14 which can be provided by being drilled out or cut out, and which, in the illustrated case, has the shape of a circle sector. At the lower part of the sleeve 10 said guide groove 14 is extended into a bayonet groove 16 having a first vertical part 16a and a mainly horizontal part 16b extending therefrom over a soft curvature and preferably having a slightly inclined bottom surface and an upper surface which is correspondingly mainly inclined correspondingly. For manufacturing technical reasons the bayonet groove 16 extends entirely through the sleeve wall but meets the guide groove 14 at the inner side of the sleeve 1. In figures 2-6 the guide groove 14 is shown with the shape of a circular sector, which shape if provided by means of a drill or a rotatable milling cutter. The drilling can be made either before or after the cylindrical bore 12 of the sleeve 10 is provided. In case a wider guide groove 14 is wanted this can be provided in that two grooves 14a and 14 b are drilled or milled out aside of each other as shown in figure 7. There is also a possibility of milling or grinding off the top 14c which is formed intermediate the two grooves 14a and 14b, whereby the bottom 14d of the guide groove is formed substantially flat, as shown in figure 8. Alternatively the guide groove 14 can be formed with sharp edges as shown in figure 9. When the apparatus according to the invention is to be used bores are provided adjacent the sides and/or the rear end of the load platform or a support frame of a transport vehicle, which bores are circular and have a diameter which is the same as the outer diameter of the sleeve 10, and the sleeve is weld connected to the load platform. The post 10 is let down into the bore 12, see figure 4, and thanks to the shape of the bayonet groove 16 the post slides down into the bore 12 of the sleeve while being rotated, so that the locking pin 5 becomes positioned adjacent the end of the bayonet groove 16, as shown in figure 5. A releasing of the post is simply made in that it is rotated, in the illustrated case counter clockwise, and it is lifted up from the post bore. REFERENCE NUMERALS 1 sleeve 2 central bore 3 post 3a lower post part 3b upper post part 4 vertical guide groove 5 pin 6 bayonet groove 7 rib 8 weld joint 10 sleeve 12 cylindrical bore 14 guide groove (a, b, c, d, e) 16 bayonet lock groove 16a vertical part 16b peripheral part