Don't use 'solid' bait as it will just pick it up and leg it. Peanut butter works for me as they have to stop in their tracks to eat it or a little pile of small grain bird seed if that's what they/it are used to. Is it usually out in the daytime ? Note what time if you can, they are creatures of habit. Now, if it is a daytime rat, there are most likely more around as the dominant ones push the smaller/weaker ones out in the day to leave safer/richer pickings after dark for themselves.
Having said all that, I've caught many in a standard rat trap at home once I've Sussed there runs which is usually alongside a wall or fence.
Good luck Mel and let us know how you get on
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