Shop Dust fan

Today I finally did a little something about the dust in the shop as well as getting some air circulation on a hot day.
I installed two box fans with house filters on top that help to alleviate most of both problems.
Box Fan....  amzn.to/2IY0aXj
Filters.....    amzn.to/2s1Tg9y

First I measured the box fan, it came out to 20 and a half inches.  The space between the rafters is 22 and a quarter. So by adding a filler 2x4 gives me the correct spacing to attach the fan between two rafters.

Next I temporarily attached a helper board with some clamps to help hold the fan up while I attached it to the rafters.

Clamps........    amzn.to/2s1OyIZ

Taking the front screen off I drilled 4 holes, two on opposite sides that the screws go through to fasten to the beams. 

After being secured I took down the helper board and put the front grill back on. I then put the 20x20 filters on top facing the correct direction and put two pieces of painters tape on each fan to hold them in place when the fans are not running.