Instruct: Classify a given review into positive or negative sentiment.
Query: Works perfectly but difficult to install

I bought this as a replacement board for a 10 y/o opener. The original board was permanently fastened to the opener chassis and had to be cut off. I then had to drill holes in the side of the opener and fasten the new board with two screws. Unfortunately Liftmaster uses the same exact stock numbers without indicating that there were changes made. In the end it works perfectly but is no job for amateurs.