Ive ALWAYS tried to find a terrier without the box before its brought in to verify .Listen at holes first ,this will give you roughly the general area .Hands flat on the ground will give you another clue up to a depth of about 6 foot ,covering the ground in 3 foot moves ,anything deeper and its back to the holes ,scramble in and turn your head about to get the direction to trench in.Open your mouth slightly as this will give you direction in one ear better than the other . Clear away the leaves, grass,twigs anything that will get you nearer the ground and listen with one ear shut .Loud baying