Here the inner carcase has been withdrawn, and another carcase within (like Russian dolls) has also been taken out.
Panels, which run in tapered sliding dovetail grooves, slide out to reveal more secret compartments.
Another panel, whose catch is released by a pin through a hole, slides away to reveal another carcase.
You can appreciate that these secret compartments can only be demonstrated as a special offer, and by someone who knows what they are doing. Part of the point of the Dummies' Guide was so that more staff at Temple Newsam House would know how to demonstrate the secret compartments correctly and safely, so hopefully this will become a regular tour feature.