in any feasible manner for example it is quite easy and satisfactory to drill a hole 20 through the bottom plate 12 and provide it with a fitting 23 for attaching a flexible hose 24 which is coupled to a pressurized tank 27 which contains a detectable gas e g a fluorinated hydrocarbon three after the fluorinated hydrocarbon has been introducted under the bottom plate 12 the detection for any leaks is carried out by scanning the upper surface of the bottom plate 12 with a gas detector 28 as indicated the detector 28 may be handled manually for the scanning operation while the detectable gas and detector employed might take various forms it is preferred to employ a fluorinated hydrocarbon as the gas and to use a halogen detector for example a detector manufactured by tif instruments inc 3661 northwest 74th street miami florida 33147 such a detector is designated as a tif 5000 automatic halogen leak detector it will be appreciated that some precautions should be taken in carrying out the method such as the need to ventilate the inside of the tank 11 with fresh air of course if forced feed air masks are used by personnel carrying out the scanning operation the ventilation may not be necessary it may be noted that the halogen gas employed is preferrably that known by the trade mark freon which is a non toxic non corrosive non flammable gas and will not affect the personnel in small concentrations.