This fan holder is meant for RAMPS 1.4 boards with the smart adapter. The fan is placed directly over the most stressed stepper modules (extruders, x and y axis) and blows also on the mosfets and the fuses.
To meet the cooling requirements for the stepper modules it induces at leased an slight air flow beneath the modules (see datasheet of A4988 and DRV8825).
To prevent the mosfets from short cuircuit there is a pin witch seperates the tabs of Q2 and Q3.
You need a 40mm fan (I used an 20mm high one) and three 40x3mm Screws.
The fan is just pressed in, but an additional cable tie can be instaled.
The hole at the middle stand of can be used for an cable driller.
This holder is designed for my RAMPS Holders:
http://www.thingiverse.com/thing:2169986 but might also fit with other assembly's.
=> This Part is used in my Prusa i3 Master Rework
Print it upside down with support enabled.
I recommend PETG or other material with good layer adhesion.