Certain times of the day, our south-facing garage door will not close due to the sun shining on the obstruction detector creating a false detect.  This model snaps into the standard mounting hardware for a Chamberlain garage door opener and shades the sensor from the sun without obstructing the path from the illuminator.  Simple.  Works.

To install push onto the bottom of the opening and then pinch the end together to slip under the top.  Don't use old, brittle filament - has to be able to flex to install.