platform 14 from which locating portions 28 having ribs 29 extend over the inner portion 31 sidewalls 14 have two pairs of opposing tongues 18 extending toward each other while endwalls 22 have one pair of opposed tongues 24 all tongues stand proud of platform 14 and have stepped ends 20 whose function will be described below referring still to fig2 the contact arm 40 is stamped and formed from spring metal with a first end or base 41 that is notched for reception between ribs 29 and a second or free end 42 during assembly the first end 41 is resistance welded to inner portion 31 so that second end 42 is biased away from inner portion 36 bimetal strip 48 is a conventional dished element that flips at a predetermined temperature typically from 40 u00b0 to 150 u00b0 c during assembly the strip 48 is placed in the cavity against arm 40 so that it is free and unrestrained on all sides the fulcrum plate 50 is then placed against platform 14 to capture the element 48 the fulcrum plate is stamped from aluminum with side edges 52 having scallops 53 for reception about tongues 18 and end edge 55 having scallops 56 for reception about tongues 24 the plate 50 is also formed with a raised portion 58 having dimple 59 which extends into the cavity after emplacing the arm 40 and element 48 fulcrum plate 50 is retained against platform 14 by heat staking the tongues 18 24 this is accomplished by applying heat and pressure to the stepped portions 20 the steps 20 ensure that any displaced plastic will not extend above the highest profile of the tongues an epoxy is.