One tip I will pass on....
I had half a dozen traps.
If you place the traps close to the loft hatch then proceed with caution when you open it

When triggered the traps/rat can launch a fair distance.
Also, you can do a sniff test every 2 or 3 days just by lifting the hatch slightly. A 1 day trapped rat doesn't smell, but after 2 to 3 days you'll get a slight tangy smell, best get them out when that happens, another couple of days and they are ripe

Rats are cannibalistic, another reason not to leave them in situ too long.
Also remember a carrier bag, nobody likes a dead rat being carried through the house.