【以下是原文】
The nucleotides are intended to be printed out as perimeters only, so turn off the fill plugin. Use Multiply to print more pieces at once: on a TOM I can print eight at a time (2x2 of the STL pair). I also recommend upgrading to SF44, which does filament retraction better than the default Skeinforge 35. Look up directions for upgrading online, as there are a couple of minor tricks involved.

The pieces have their letter embossed on their outer edges, but I still prefer to print them in different colors to make the sequence obvious. Remember: A's link across to T's and G's link across to C's. The snap shapes enforce this pairing. You may also notice that the A-T link is less secure than the G-C link: this is intentional, to model the fact that G-C pairs link by three bonds while A-T pairs link by only two. 

There are some odd angles involved in creating a helix out of flat pieces, so the snap links along the helix backbone are only meant to line up along the outer edg