Illustrations by Alan Batley
Fold a large square of poster board three ways and make holes along the outer edges.
Tape white paper onto the middle section, and put bait such as wet dog food in the centre.
Daub non-toxic poster paint mixed with oil on cloth/greaseproof paper at the ends as ‘ink pads’.
Tie the top together using cable ties, and check the paper in the morning for any prints.