I was waiting for some final information before posting, but will post what I am sure about now since it's slightly different than above. There are lots of ways to arrange the relay - the incoming runner grabs a map and hands it to the next runner, the outgoing runner gets their own map; the incoming runner punches a box that separates their time from the next runner's time, the outgoing runner punches a box that does this, etc. In all cases though, as noted above, each runner has their own SI card and this information is in the relay software along with which runner has been assigned to which forking of the different legs.
For this relay, each runner will grab their own map from the map board as they start (except the first leg runners who will get their maps handed to them for the mass start). So, the tag-off happens, the next leg runner grabs their own map from the map board and heads for the first control. The runner that has just finished punches a "tag-off" box and then downloads - the time recorded at the tag-off box is used as the end time for the runner that just finished and the start time for the runner just starting.
This is why we need relay teams to submit the names and SI card #'s of the people in their team as soon as possible, so we can start building the event in the software. It would be great if people would fill out and email me
this form but an email with the information (team name, point division, names of runners in order, each person's point value and SI #) is also okay. Please send to registrar@dvoa.org. Thanks!