is a fiber or plastic (originally wood) dowel used to enable the attachment of a screw in material that is porous or brittle or that would otherwise not support the weight of the object attached with the screw. It is a type of fastener that for example allows screws to be fitted into masonry walls. There are many forms of wall plug, but the most common principle is to use a tapered tube of soft material, such as plastic. This is inserted loosely into a drilled hole, then a screw is tightened into the centre. The screwing action wedges the plug firmly in place, the soft material conforming tightly to the masonry. Such fasteners can attach one object to another in situations where screws, nails, adhesives, or other simple fasteners are either impractical or ineffective. Different types have different levels of strength and can be used on different types of surfaces.