A pierced surround has no continuous outer frame to hold it together, which raises an obvious question: what is everything actually fixed to?
The answer is a core. Behind the visible carving there is a plain rectangular frame in solid teak, sized to the glass and jointed at its corners - the only fully closed member in the whole piece. It carries the plate, it takes the hanging fixings, and it is what the mirror is really built on.
Every scroll of the surround is then jointed back to that core. The long outer sweeps are not held by their neighbours - they run inward and are housed into the core itself, so each one has its own independent connection to the structure.
The alternative, joining scroll to scroll around the outside, would make the frame a chain: every element depending on the one beside it, and a knock at any point loosening several.
Fixed to a core, a damaged scroll is one scroll. And because the core is a plain rectangle, the mirror hangs square from two points on solid timber rather than from carving.