This is a clamp-on guide for cutting 2-inch PVC pipe (should work for ABS as well). It will help you to make a straight cut with a hand-saw without having to use a miter box.

To use, slide onto the pipe and then clamp on the thinner part of the ring. Clamping is not strictly necessary. Then slide the saw right against the edge of the ring.

If you need to cut a different pipe size, see the Instructions tab.

Prints in 1hr at 0.3mm layerheight with no support. Designed in Autodesk Fusion 360.

I printed this on a Replicator2 at low quality (0.3mm layer height), with no support. The cutting surface is oriented upwards to keep it flat, if you put it on the build plate it will be somewhat warped.

To print for another pipe size, you can just scale the model. Measure the outer diameter (OD) of your pipe in mm, and use the following formula:
scale_value = (OD + 0.6) / 61
(multiply by 100 if you need a percentage)

If you don't have calipers to measure, you can look up standard pipe sizes here: http://en.wikipedia.org/wiki/Nominal_Pipe_Size