such as by screw 47 or by adhesive magnet housing 46 is made of a ferromagnetic material such as steel or nickel ceramic magnet 45 is attached to magnet housing 46 magnet housing 46 includes ridges 41 that protrude beyond the surface of ceramic magnet 45 and other parts of central portion 31 when brush 90 is attached to clip 10 ferrule 91 contacts only ridges 41 because magnet housing 46 is composed of ferromagnetic material the contact with ceramic magnet 45 induces magnetic force in magnet housing 46 which attracts ferrule 91 in addition to the magnetic interaction of ridges 41 and ferrule 91 mechanical interaction between ridges 41 and horizontal ridges 93 of brush 90 prevents brush from slipping vertically downward relative to magnet means 40 preferably ridges 41 protrude beyond all other parts of central body 31 farther than ridges 93 protrude from all other parts of ferrule 91 such that only ridges 41 can contact ferrule 91 when brush 90 is attached to clip 10 each contact portion 37 of prongs 33 34 includes a generally planar contact face 38 as best seen in the bottom view of fig7 contact faces 38 are inclined at mirror image angles from being parallel to the plane of body 30 this inclination allows.