A biogas holder is generally a floating cover with an extended rim that is submerged into the water level adequately so as to ensure that in the maximum lift position of the floating cover the rim still remains below the top water level. The covers for gas holders are designed with a vertical guided system. The rollers are attached with the cover of gas holder around its peripheral. This ensures that the cover of gas holder covers around its peripheral to ensure that the cover is rightly balanced during the lift position and is not tilted unduly under the conditions of wind load. The properly sized structure is designed to ensure the roller guidance above the gas holder tank area.