A mosaic glass technique allowed multiples of an image to be created: a figural or design composition was made by bundling colored glass canes, which were then drawn out into a long bar. The bar was then sectioned at right angles, probably by striking the bar with appropriate tools, to produce small inlay tiles. The tile would then be smoothed and polished on the face intended to appear outwards.
Such elements could also be used side by side to create repeating patterns. Or if the rod presented one half of an element that was symmetrical, such as a face, a tile and a reversed tile from the same rod could be put together to form a complete whole, as here.Link to a blog about Ptolemaic Art at The MetNile and Newcomers: A Fresh Installation of Egyptian Ptolemaic Art