One of the best ways to keep foxes,cats,dogs out of your garden is to prevent them getting in in the first place. Prickle strips are designed to give maximum discomfort with minimum harm.

Made from weather resistant polypropylene, Prickle strip is easily attached to the top of a fence or brick wall with glue, nails or screws (see instructions below). Can also be used on tree branches or sheds. Easy to cut and drill more holes if required.

Supplied in strips 50cm (1ft 71/2 inches) long by 4.5cm wide (1 3/4 inches wide). The strips are hinged (see picture below) to allow a better fit to curved surfaces. 
Put two strips side-by-side to get more width. Or cut down length ways for more narrow fence-tops (see below)

Also a very effective cat and human intruder deterrent, seen on BBC's 'Beat the burgler'.

Fitting Instructions:

Many glues and adhesives will not adhere to polypropylene - use Pink Grip Adhesive or screws / nails

Trimming:

Trim to size using a suitable saw. Curves and bends can be formed by immersing in very hot water. Prickle Strip can also be easily cut (using scissors or a knife) to a double or single row strip using the hinge grooves as a guide