The mask shield is NOT substitute, rather an additional level of defense in-order to extend the lifespan of disposable style facemasks..  This is a shell or guard, worn over the mask intended to minimize direct exposure to moisture.

It is reccomended to afix bands or straps using the slits on the side of the maks. If none are available, carefully hook the elastic mask straps around the hooks to secure the 2 together, be sure to double check mask to face seal after device is applied.