Regular acoustic guitars have a "heel block" fixed in the body, from which the solid neck extends along to the headstock or peghead.

On a Hollowneck guitar, the heelblock is effectively pushed all the way up to the peghead, becoming a single piece known as the "headblock".
The sides of the body extend all the way along and are fixed to the portion of the headblock which is concealed within the hollow neck..

It's this extension of the resonant chamber which makes Hollowneck guitars able to produce such a beautifully rich and vibrant tone.

 

Headblock with veneer face

The air pressure waves produced by the soundboard reverberate throughout the hollow interior, resulting in the distictive sweet woody sound.

When you strum one of these, it comes alive! ...quivering and purring in your lap like a well-fussed cat.

Alan's build showing the tailblock & sides attached to the headblock.

Traditionally the bracing of the top follows a variation of the "X-brace" found in many other designs of steel-strung guitar.

Soundboard bracing

 

 

Photo: The Knutsen Archives

Some are "Ladder-braced" like the Hilo hollownecks made by the Oscar Schmidt Company, some floating-bridge hollownecks and the rare ladder-braced Weissenborn pictured above.

Bridge with straight saddle-piece

The bridges most often have slot for the saddle-piece cut straight rather than with the customary "compensation angle".

Regular guitars suffer from intonation problems when playing the bass strings fretted higher up the neck.
Pushing the string down onto a fret can push the note sharp and for this reason the bass strings are made slifghtly longer than the treble strings to cancel this out.

The nature of Steel Guitar means that this compensation is considered less necessary, as correct intonation is determined by bar position and pressure rather than the fixed position of a fret.