Abstract: A mask for laser sealing a temperature and environmentally sensitive element, such as an OLED device, surrounded by a frit wall between first and second substrates. The mask is opaque and has a transparent elongate transmission region. The width of the transmission region may be substantially equal to the width of the frit wall. A strip of opaque mask material extends approximately along a longitudinal center line of the elongate transmission region. The mask is located between a laser and the first or second substrate. The laser emits a generally circular beam having a diameter that is larger than the width of the frit wall and is directed through the transmission region in the mask, such that opaque portions of the mask block portions the laser beam and the transparent transmission region allows a portion of the laser beam to pass through the mask and impinge upon the frit wall to melt the frit wall, thereby joining the first and second substrates and hermetically sealing the element therebetween.