Chamberlain 1145-1/3HP - Manual (Page 10)

INSTALLATION STEP 1
Position and Install Header Bracket
Installation procedures vary according to garage
door types. Follow the instructions which apply to
your door.
THE HEADER BRACKET MUST BE RIGIDLY
FASTENED TO HEADER WALL. REINFORCE
WALL WITH A 2x4 IF NECESSARY. FAILURE TO
COMPLY MAY RESULT IN IMPROPER
OPERATION OF SAFETY REVERSE SYSTEM
(SEE PAGE 22).
SECTIONAL DOOR & 1-PIECE DOOR WITH TRACK
1. Close door and mark the inside vertical centerline of
garage door. Extend the line onto header wall above
door.
2. Open door to highest point of travel as shown. Draw
an intersecting horizontal line on header wall 2" above
high point. This height will provide travel clearance for
top edge of door.
NOTE: When the headroom is not sufficient for 2"
clearance, the bottom edge of bracket may be placed
in line with the door's high point of travel.
3. Position bracket as shown (centered on vertical
guideline with bottom edge of bracket on horizontal
line).
Mark either top and bottom or left and right bracket
holes. Drill 3/16"
pilot holes and fasten bracket.