This manifold bracket comes fitted with checkvalves per ball valve outlet. Each check can also be removed if you want gas or water to move freely in all directions. 

Using a thin flat headed screw driver, simply slide/pop the black retainer tabs and remove the ball valve
The duotight 8mm 4 way manifold is complete with mounting capabilities out of the box using button head screws. 8mm (5/16) duotight x 4 Way Manifold with Check Valves & Isolation Valves

it is important to cut the hose straight for a good seal.