Chamberlain 1265LMC 1/2 HP Owner's Manual page 20

INSTALLATION STEP 11
Fasten the Door Bracket
NOTE:
Metal or light weight doors using a vertical angle
iron brace between the door panel support and
the door bracket:
Metal, insulated or light weight factory reinforced
doors:
Wood Doors:
NOTE:
To prevent damage to garage door, reinforce inside of
door with angle iron both vertically and horizontally.