What does top and tall mean when fishing maggots?

Top-and-tailing is simply a way of hooking two maggots, one through the fatter ‘tail’ and one through the pointed ‘head’.

The main advantage of hooking two maggots in this way is that they don’t tend to spin as you retrieve. 

Two maggots hooked traditionally through the fat tail end will act like a propeller on the retrieve, causing your line to twist which will result in tangles.