LiftMaster K77-37857 Gray Cover for RSL12U Slide Gate Operators
The LiftMaster K77-37857 is the gray operator cover used on the RSL12U family of residential slide gate operators. The cover is an important enclosure part because it shields the operator's electronics, battery area, wiring, and drive components from rain, dust, lawn sprinklers, insects, and sun exposure. A damaged cover may allow moisture into the operator or leave the unit looking unfinished and unsecured. This cover is specific to RSL12U / RSL12UL style slide gate operators and should not be swapped with RSW12U swing operator covers or larger commercial CSL/CSW covers. If the old cover color, lock area, or label layout differs, verify the part number by diagram before upload or ordering.
Compatible With
- LiftMaster RSL12U residential slide gate operators
- LiftMaster RSL12UL residential slide gate operators where the parts diagram calls for K77-37857
- RSL12 residential slide gate operator cover applications using the gray cover
- Not for RSW12U, CSL24U, CSW24U, LA400, LA500, or SL3000 operators
Features and Specifications
| Manufacturer | LiftMaster |
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| Product Type | Gray operator cover |
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| Part Number | K77-37857 |
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| Application | RSL12U / RSL12UL cover replacement |
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| Compatible Operator Type | Residential DC slide gate operator |
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| Color / Finish | Gray |
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| Included Components | Cover only unless current listing states otherwise |
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| Notes | Also searched with K77-37855 in some listings |
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Also Known As / Related Part Numbers
- K77-37857
- 77-37857
- K77-37855
- LIF-K77-37857
- LM-K77-37857
- K77 37857
Technician Note
RSL12U and RSW12U covers are easy to confuse by name, but one is for slide gate operators and the other is for swing gate operators. Always match the model tag before ordering.
Before Ordering
- Confirm the operator model is RSL12U or RSL12UL.
- Verify the cover color and shape against the original housing.
- Check whether the old cover is gray or another finish.
- Inspect the lower enclosure for cracks or damaged lock points.
- Confirm whether related number K77-37855 appears on the parts diagram or supplier listing.
Important Ordering Warnings
- Do not use this as an RSW12U swing gate cover.
- A replacement cover will not repair water-damaged electronics inside the operator.
- Do not ignore missing warning labels or damaged access-lock hardware.
Professional Advisory
For commercial gate operator repairs, verify the model, wiring, mechanical condition, and all required entrapment protection before returning the system to service.
Product Questions and Answers
What does K77-37857 fit?
K77-37857 is commonly listed for LiftMaster RSL12U and RSL12UL residential slide gate operators.
Is K77-37857 gray?
Yes. Public listings identify K77-37857 as a gray cover for RSL12U applications.
What is K77-37855?
K77-37855 appears as an also-known-as or related cover reference in some listings. Verify by parts diagram before treating it as the same part.
Will this fit an RSW12U swing gate operator?
No. RSW12U uses a different swing gate operator cover. RSL and RSW covers are not automatic substitutes.
When should this cover be replaced?
Replace it when the original cover is cracked, missing, badly weathered, will not lock, or no longer protects the operator internals.
