FPI FP90 Owners & Installation Manual page 24

WARNING: KEEP MASONRY MATERIAL AT LEAST 1/2" (13mm)
FROM THIS TOP FACING GUIDE. THIS IS REQUIRED
TO PREVENT MASONRY FACING MATERIAL FROM
HITTING THE TOP STIFFENER LOCATED ON THE BACK
OF THE SURROUND WHICH IS HIGHER THAN THIS EDGE.
INSTALL THE SURROUND TEMPLATE ONTO THE UNIT
WITH THE SAME MOUNTING SCREWS AS THE SURROUND.