Chamberlain HD420EVP Owner's Manual page 7

Assembly
STEP 2 Fasten the rail to the motor unit
To avoid SERIOUS damage to garage door opener, use ONLY those bolts/fasteners mounted in the
top of the opener.
1. Insert a 1/4"-20x1-3/4" bolt into the cover protection bolt hole on the back end of the rail as
shown. Tighten securely with a 1/4"-20 lock nut. DO NOT overtighten.
2. Remove the bolts from the top of the motor unit.
3. Use the carton to support the front end of the rail.
4. Place the "U" bracket, flat side down onto the motor unit and align the bracket holes with the bolt
holes.
5. Fasten the "U" bracket with the previously removed bolts ; DO NOT use any power tools. The use
of power tools may permanently damage the garage door opener.
6. Attach chain spreader to the motor unit with two screws.
Bolt 1/4"-20x1-3/4"
HARDWARE
Lock Nut 1/4"-20
Bolts (Mounted in the
garage door opener)
"U" Bracket
Bolt 1/4"-20x1-3/4"
Cover
Protection
Bolt Hole
Lock Nut 1/4"-20
6
Hex Screws
8-32x7/16
Chain
Spreader
SLIDE RAIL TO
STOPS ON TOP AND
SIDES