Wentletrap is a spiral staircase, and also a seashell which has the same look of spiraling steps. Wentletredes is perhaps a cognate. I suspect that it refers to steps winding upwards with no outside railing for the hands (but on a lighthouse I would want to cling to something!) This architectural feature is often found inside old churches as a way to get up to the organist's loft or whatever. Muuranker sounds like wall-anchor (murals usually being vertical) so those rings are probably on a vertical surface. Spikes and nails are different in size and heft. Also spikes tend to be removable and to stick out more from a surface than do nails. Spikes also sometimes have bent tips, or holes for ropes, whereas nails are usually straight and uncluttered. I'm glad that somebody else recognized the name Fresnel, and if this lighthouse really does have a fresnel lens modeled as part of it, it is exceptionally well-detailed. Carolly