The Caperer Size 14 is a dry-fly imitation of the autumn caddis known to anglers as the Caperer. On UK rivers it is most relevant around September, when these substantial sedges can bring trout to the surface, although timing varies with river and weather.
Fish it close to banks, below overhanging cover and through glides where adult caddis are active. A natural drift is the starting point, but a short lift or skate can be effective because adult caddis often move across the surface. Match the hatch rather than fishing it purely by date, and look for the naturals before selecting the pattern.