This simple part can be used as a prime pillar for dual extrusion prints.
Place a copy of this pillar on either side of the part in your favorite slicing program. Scale the pillar in Z-direction to match the height of your part. The pillar is 10mm high to make scaling easy. For example, if your part is 25mm high, scale the pillar in Z-direction 250%.
The pillars will be printed together with the part and make sure the extruders are wiped and kept primed at each layer.
Make sure to place the pillars at least at a distance from the part that is greater than the distance between the nozzles, otherwise the nozzles will wipe clean on the edge of the part.
Visit my blog Uptimefab.com for a more detailed description on the use of the pillars.
The sample part in the picture is a dice model From thingiverse, part no. 21842