Initial proposal at C&A Meeting: http://www.slac.stanford.edu/exp/glast/ground/LATSoft/vol1/geometry/notes/GeoApril2007.pdf See Slide 7
When Joanne modeled the tiles as depicted without changing anything else Joanne realized there would be a gap along the edge where the sides come together for rows 1 and 3 so she modified the design by making the width of these rows greater. You can see some more pictures at http://www.slac.stanford.edu/exp/glast/ground/LATSoft/geometry/pictures/ACD/newSides/
From Alex, for our information, in reality the corner gaps between the adjacent sides tiles are 4mm in nominal.
Next up: Modifying side ribbons to follow contours of new side tiles.