Neck Joint - Set In Neck

Set-in neck is a method of guitar (or similar stringed instrument) construction that involves joining guitar neck and body, pressing it tightly together using some sort of adhesive. It is a common belief that this yields a stronger body to neck connection than a bolt-on neck, although most luthiers agree that a well-executed bolt-on neck joint is equally as strong, and will have similar levels of sustain and neck to body contact. However, neither of these joints are as strong as a neck-thru body joint, which is a labor and material intensive undertaking and is usually only seen on high end offerings.

This method is most popular on acoustic guitars. Almost all major acoustic guitar manufacturers use set-in necks, with only notable exception being Taylor Guitars. In the electric guitar market, Gibson traditionally produces almost all of it's electric offerings as set-in neck models, as opposed to rival Fender, which traditionally builds it's electric instruments (most notably, the Stratocaster, Telecaster and various Electric Basses) with bolt-on necks.

Wooden musical instrument construction relies on four widely used types of glues:

• Hide glue
  
• PVA (both "white glue" and "yellow glue")
• Epoxy and Cyanoacrylate are sometimes also used for neck joints, but generally such use is rare. Structure of these glues makes it difficult to disassemble joint later if repair or servicing is required

Typically cited advantages of set-in neck include:

• Warmer tone
• More sustain, although this is not supported by formal research
• Usually better access to top frets in comparsion to bolt-on necks utilizing a metal plate (as seen on Fender guitars)

Disadvantages

• Slightly harder to mass manufacture than bolt-on necks, much harder to repair / service than a bolt-on neck
• The player has no control over the neck-to-body angle; changing it requires disassembling the instrument and re-glueing the neck by an experienced luthier

source : Wikipedia