Why not set out helmets on the ramparts, and pikes as well as guns?
It was a good idea.

He hurried to the armoury, and quickly took from their places all the steel helmets and pikes and plumes on which he could lay his hands.

These he artfully disposed on various parts of the battlements, so that to any one below it would appear that instead of one man, twenty armed warriors guarded the place.
"Who knows but these numskulls may serve me in good stead ?" said the youth to himself, laughing to think what excellent substitutes for a living man an empty helmet with a spear-head beside it may be made to appear.

This little artifice being satisfactorily accomplished, and lights set burning in various rooms of the castle still further to aid the delusion, he returned once more to the east terrace and began his solitary vigil.
The moon was up, and peeped occasionally from behind the drifting clouds to light up the dark scene below.

As Singleton peered down from his lofty post, he could see the water sparkling below him, and catch the distant lights here and there on wood and mountain.