the present invention discloses a unique method of manufacturing a flashlight head assembly that is completely self - contained and includes a waterproof switching mechanism and an inline flashlight sealing assembly that is provided in an interior cavity of the flashlight . the sealing assembly is an integral component of the flashlight head thereby creating a monolithic waterproof seal . the method of assembling the flashlight head includes providing a housing having an outer wall and a front wall , inserting an interior mounting assembly that cooperates with the housing to form an interior cavity and filling the interior cavity with a sealant material .