AS I built my Anet A8, I knew I would need to add something to control the wiring and electronic components. I used mosfets on both the heatbed and extruder. Due to its overall length, I had to print it in two pieces; then, I used a filament pen to 'glue' them together.
Edit 2017-02-28: Added STLs and photos of cover and fan. The top section overlaps the bottom section so screws go through both at two positions. There are two STLs. I imported both to S3d and printed them at the same time.
I adapted the designs from the following members to make what I needed.
I imported the STL to SketchUp and modified it to suit my needs.