Abstract: The invention relates to a passable closing system for a door or window opening, comprising a length of a first flexible material, which is fixed to supporting members that can be connected to a door or window casing surrounding said opening. The supporting members are made up of at least one strip-shaped member of a second flexible material, which is fixed to said length of material, and which can be detachably connected to the casing. Preferably, a strip-shaped member fitted near the upper side of said length of material is connected to said casing at a point located near one end of said strip-shaped member and at a point located between the ends of said strip-shaped member.