How do you set the dwell on an old school mallory points distributor?

i always had a meter with dwell on it you adj your points base and keep the gap the same

Addition to above:

Haven't messed with a points ignition in quite some time, but still have a Sun distributor machine and remember how to do it, if it's a dual point distributor the easiest way is to block one of the sets of points with a matchbook cover or thin piece of cardboard in between the points and set the dwell on the other set, then put the matchbook cover between the point set you just set the dwell on and set the dwell on the other set, then remove the matchbook cover and your done. If you're doing this on the car (as opposed to doing it on a distributor machine) you should then re-set or at least check the timing.