Chamberlain 248730 - Manual (Page 6)

5
Assembly
STEP 1 Assemble the rail and trolley
To prevent INJURY from pinching, keep hands and fingers away from the joints while assembling the
rail.
To avoid installation difficulties, do not run the garage door opener until instructed to do so.
The front rail has a cut out “window” at the door end (see illustration). The hole above this window is
larger on the top of the rail than on the bottom. A smaller hole 3-1/2" (8.9 cm) away is close to the rail
edge. Rotate the back rail so it has a similar hole close to the opposite edge, about 4-3/4" (12 cm) from
the far end.
1. Remove the straight door arm and hanging bracket packaged inside the front rail and set
aside for Installation Step 5 and 9. NOTE: To prevent INJURY while unpacking the rail
carefully remove the straight door arm stored within the rail section.
2. Align the rail sections on a flat surface as shown and slide the tapered ends into the larger
ones. Tabs along the side will lock into place.
3. Place the motor unit on packing material to protect the cover, and rest the back end of the rail
on top. For convenience, put a support under the front end of the rail.
4. As a temporary stop, insert a screwdriver into the hole 10" (25 cm) from the front end of the rail,
as shown.
5. Check to be sure there are 4 plastic wear pads inside the inner trolley. If they became loose
during shipping, check all packing material. Snap them back into position as shown.
6. Slide the trolley assembly toward the screwdriver as shown.
7. Slide the rail onto the “U” bracket, until it reaches all the stops on the top and sides of the “U”
bracket.
To garage
door opener
(TO MOTOR UNIT)
Front Rail
Section
(TO DOOR)
“U” Bracket
Outer Trolley
Inner Trolley
Wear Pads
Rail
Tab
Trolley
Window
Cut-Out
SLIDE TO STOPS
ON TOP AND
SIDES OF
“U” BRACKET
Idler
Pulley
Hole