is pressed by the spring 7 pushes a lower end part 6d of the connecting tube 6 39 in a state with an engaging piece 6c of the upper connecting tube 6 39 caught so that the joint b would be fixed to a straight form upon unfolding the joint b thus the frame member can be unfolded to a straight form or can be folded up around the sleeve 8 there are formed several holes 8h so that foreign materials such as sand inadvertently introduced can be removed as shown in fig7 the bent joint c is constituted such that connecting tubes 9 and 9 39 with the rods 1a coupled there are movably coupled through hinge plates 9a and 9a 39 and a supporting shaft 9b so as to serve as a joint on the movably coupled part of the upper connecting tube 9 there is formed a coupling projection 9c extending from a lower end part 9e of the upper connecting tube 9 on the movably coupling part of the lower connecting tube 9 39 there are formed an inclined face 9d and an inclined end 9e 39 with a certain angle about 35 u00b0 45 u00b0 on the inclined face 9d there is formed a recess 9c 39 into which the coupling projection 9c is fitted therefore as shown in fig8 if the connecting tubes 9 and 9 39 are pushed outwardly the tent is folded up if the connecting tubes 9 and 9 39 are pushed inwardly then the joint c is unfolded with a certain angle as shown in fig7 that is the projection 9c is firmly coupled into the recess 9c 39 and the lower end part 9e of the connecting tube 9 is firmly coupled with the inclined.