means 2 is shown comprising the mobile unit 12 having a wheel 44 and an extractable connecting device 16 the mobile unit 12 comprising a wheel is fixedly attached to the connecting device 16 the connecting device 16 is arranged in such a way that it can be extended for example with a hand turning wheel 48 which is connected to a screw mechanism adapted to enlarge or decrease the length of the connecting device also a pneumatic or hydraulic telescope mechanism can be employed by extending the length of the connecting device 16 the upper part 42 of this device can be safely linked to the connecting clamp 14 only partially depicted which is fixed to the valve 8 the position of the connecting device 16 and the mobile unit 12 can be manually adjusted in a very precise manner in addition as a foot guide for the mobile support means the rails 46 can be placed on top of one or more wooden planks in order to prevent the underlying surface 10 e g of a scaffold from damage in fig5 the assembly according to fig1 can be seen from above two rails 46 are aligned in parallel each rail being besides the valve 8 two mobile support means 2 and 4 are located at the back part 6 of the valve 8 and are attached to opposite sides the mounting rail 22 is centrally located between both rails for the mobile support means however above the valve 8 the length of the mounting rail 22 essentially corresponds to the length of both rails 46 as soon as the valve 8 is removed from the tube system it can be placed on a trolley 50 and.