With manual timing, when you get two close finishers, you need to record two times as close together as you can manage. It's an interesting question how close you can get them.
For Head races using manual timing (with stopwatch, tablet or timing device) we rely on our reaction times to get accurate times for each crew. Here are a few sites to test your reaction times:
The Pairs Head is an interesting race to time, with a lot of starters over a fairly short course. The shorter course means that crews are closer together in times.
I was a volunteer timer on the Start at the Pairs Head on Saturday 10 Oct. The Chief Timekeeper is Sarah Powell, also in charge of entries, and also racing on the day, so quite an achievement on her part.