My kids have a lot of pens, and like LEGO. So this seemed like the perfect combo.
This is a pen holder designed to be built into your own LEGO creation. Make it as small or as big as you want. Choose if you want studs around the base, top, both or no studs at all (which is just crazy...). And you don't have to store pens in it, you could make smaller holes and put screwdrivers in it or just one giant hole to keep all your pens. It's all up to you, use the customizer to create your own pen holder. A few samples can be found under the files section though.
The generated stls are complex and the print time becomes quite long. I might try to fix this in an later update
Depending on material and printer you might need to tweak the margin settings in the customizer to get a snug fitting of the LEGO studs