The primary protrusions 40 and the secondary protrusions 42 also prevent or at least minimize the possibility of the magnets 22 decompressing and returning to an original/relaxed state and applying a tensile force on the adhesive 50 when the clamp or other retaining means is removed. [0033] The secondary protrusions 42 are preferably dimensioned so that a single secondary protrusion 42 can support