Abstract: A method of hermetically sealing by NVFE (non-vacuum focused energy) welding abutment joints formed by elongate surfaces. At substantially spaced intervals narrow shallow vent grooves are formed across one of the surfaces, while leaving between the vent grooves separating lengths of many times the length of the groove width. The grooves enable the NVFE welding to be effected continuously in unidirectional pass along the joint, the gases venting from the joint through the successive vent grooves as the welding progresses continuously along the joint. Continuously after the venting of the gases at each of the successive vent grooves, each vent groove is sealed by the NVFE welding without interrupting the welding progression.