The answer to your question is Yes, but only by user efforts to add the taper.
The tool doesn't have a built in taper, if that is what you are asking. the person doing the filing must adjust there filing to get a tapered base rail when finished.
This can be done in the slot, or after you pull the rail from tool. I usually do my taper in the slot, filing down to bottom of slot on the end needed.
The same slot is used for both left and right rails, so it is flat at both ends with no taper built in.
Hope this helps answer what your question is.
Kurt K, Training in Oklahoma