the sheets are also so shaped and welded as to provide a terminal flap 26 at the closed end of each transverse tube 8 press fasteners 28 are provided on the flaps 24 and 26 so that two of the arrangements shown in fig3 may be interwoven as illustrated in fig1 and 4 thus a second arrangement re oriented by rotating fig3 through 180 degrees in the plane of the paper has its transverse tubes 108 interspaced with the transverse tubes 8 as illustrated in fig1 in the second arrangement features corresponding to those of the first arrangement shown in fig3 are identified by a reference number formed by adding 100 to the number used in fig3 as may be seen from the drawings the second transverse tube 108 pass beneath the first longitudinal tube 2 referring to fig4 the terminal flap 126 at the end of each second transverse tube 108 is secured to the marginal flap 24 of the first longitudinal tube 2 by means of corresponding press fasteners 28 and 128 the marginal flap 24 is secured to the cover 6 by further press fasteners 30 the transverse tubes 8 pass beneath and are secured to the longitudinal tube 102 in a similar manner as may be seen from fig1 and 2 the arrangement produces a shallow 34 v 34 shape between the transverse tubes 8 and 108 since this wraps round the patient rather more than the flat beds of the prior art it spreads the contact area so reducing the pressure and increasing the patient 39 s comfort the 34 v 34 shaped arrangement also.