threaded cooperating relationship between adjustment nut 53 and piston 54 as piston 54 moves upwardly it moves elongate member 36 of upper end 30 upwardly until ceiling engaging surface 32 abuts against ceiling surface 70 at this point further rotation of adjuster 55 results in the downward movement of adjustment nut 53 relative to piston 54 which is firmly abutted against upper end 30 with consequent compression of spring 56 as this occurs key 55a on the adjuster 55 effectively moves up the elongated slot 53a in the adjuster nut the further the nut 53 moves down the greater the compression of the spring 56 and the greater the pressure thereby exerted against the ceiling surface 70 accordingly the position of nut 53 provides an indication of the pressure being exerted by the post against the ceiling viewing the nut 53 through the slotted window 57 58 in the upper case 51 and comparing its position with reference to this slotted window e g by registration of its out turned upper ledge 53c with indicia alongside the window gives the operator an indication that the post is under enough longitudinal pressure to be safely and firmly installed but not under so much pressure that it may damage the ceiling surface the initial load capacity of spring 56 and approximate length of the post are conveniently preset on manufacture and assembly to minimize the adjustment needed on installation referring now to fig3 there is illustrated a plurality of safety support structures 10 each of which comprises a post 20 an upper end 30 a lower end 40 an adjustment means 50 and an accessory mounting region 60 further there is illustrated a plurality of horizontal support accessories 90 which are connected to accessory mounting region 60 of.