For Use with Top and Bottom Inserts
High Density Cast Body
Gaskets for Use with 3/8" or 1/2" (10 or 12 mm) Glass

This CRL American T/B Door Patch will allow you to use the same fitting for either top or bottom by simply installing the appropriate insert.
 
For Use with Top and Bottom Inserts:
PAIS for top
PAIB for bottom