An often oversight for heatsink manufacturers is that they leave the
bottom of a heatsink un-finished. Often times, it is not flat and may
actually exhibit areas of roughness. To fix this, we're going to grab
a few sheets of sand paper and start sanding and smoothing out our
heatsink surface. Now most of the time, to accomplish this, you would
need to run to the hardware shop and buy a slew of different grit rated
pieces. This can rack up a good chunk of change for just one
heatsink.