Abbreviation in survey plan

I like to understand the survey plan with some abbreviations which are unknown to me. Appreciate if someone can help with this. This survey was done in 1995 for a private property in Ontario Canada. The abbreviation that I am interested are: Fdn, Bk and Cop (or Cap).
Here is the drawing:


Fdn Most likely Foundation, the bottom or lowest part of a sloped side of an irregular cast concrete wall.
Bk Back
Cap Top Upper piece of two pieces of concrete. As if the upper piece sticks out over the lower part.

Perhaps meaning that the single plan view of the old property does not have perpendicular walls and edges of the pavement.

Above is a snippet.

@RACookPE1978, Spot on! Thank you for helping.