Abstract: The invention provides a washer having a deformable annular skirt extending from the underside of the washer. The skirt deforms to the shape of the surface to which the washer is secured by means of a fastening device having a shank passing through the washer. The resiliency of the skirt seals the cavity between the underside of the washer and the surface from moisture. The washer is particularly suitable for use with corrugated surfaces and for retaining the swarf produced by self drilling fastening devices. A snap-on cap for the washer is also provided to seal the head of the fastening device.

Abstract: Fastening assembly comprising a base, locking or anchoring element, provided with an upper annular flange, which accepts and engages a removable flexible cap or covering element formed of impermeable elastic material, preferably molded thermoplastic, retained thereon by interference fit. The components when united provide a protective and/or decorative cover for a fastening element that can extend into a sub-stratum, work-piece or material through the base element. The cap and base elements may subsequently be marginally welded together so as to safely house electronic components of telephone or computer systems against unauthorised interference.