I have been looking for an inexpensive mouse guards. I found these gutter guards at Menards. The plastic is exterior grade and the pre-drilled holes are 3/8". Trim off the one side, cut them the width of your hive opening, fasten with 6 screws and your done.

Quick, simple, cheap.

Not sure how the plastic will hold up to vermin....guess we will see.

Why would I not just leave them on all year long?

Couldn't get my photos to upload. Here is the product: http://www.menards.com/main/building...498-c-5812.htm