"r" shaped structures

Small concrete structures in the shape of the letter "r" have been found in many places around Hong Kong Island. As the number of places they've been found keeps growing, it's becoming more difficult to keep track of them so I've created this Forum Topic as a central reference point.

Here's what we're talking about.

So far, they've been found at the following locations;

1. South Bay, around the site of Pillbox and Lyon Light 20 (my post of 3-3-2015 at www.gwulo.com/node/19380), 

2. Little Turtle Bay, around Pillbox and Lyon Light 30 (my post of 12-3-2015 at www.gwulo.com/node/1953),

3. Middle Bay, around one side of the site of Pillbox and Lyon Light 19 (my post of 12-3-2015 at www.gwulo.com/node/2034),

4. Above Wong Nei Chung Anti-Aircraft Battery (Davids pic of 3-2-2016 and my post of 27-4-2016 at www.gwulo.com/node/19380),

5. The south side of Wong Nei Chung Reservoir (my post of 22-10-2016 at www.gwulo.com/node/35061),

6. Above the military bunkers on the west side of Aberdeen Upper Reservoir (my post of 8-11-2016 at www.gwulo.com/node/32367).

Despite their large numbers there is some doubt about their function or functions. The two most popular suggestions are anchor points for barbed wire entanglements that surrounded WWII military structures and key points, or markers for underground electricity or telephone cables.

At this stage I'm inclined more towards the military fence option, but on the downside note that "r's" seem not to be present at some sites where they would logically be expected, e.g. the pillboxes at Jardines Lookout. In a number of places the "r's" run in parallel lines on both sides of lines of concrete fence posts, e.g. 2, 3 & 5 above. In these instances I can't think of any function for them other than strengthening millitary fences by anchoring barbed wire. However, when concrete fence posts are absent, the "r's" function is not so obvious. Regarding the possibility of them being underground cable markers, I've yet to see any evidence of cables in the vicinity of "r's" - but perhaps that's not surprising if the cables are still underground.

The more "r's" we come across, the more confident we'll be of correctly determining their function or functions. So if you do find any whilst out walking, please feel free to describe what you've seen here. Remember to look for evidence of concrete fence posts, military structures, cables or anything else that seems relevent in the vicinity.