two different woods

[Lonewolf]

When a guitar body is said to be made of both mahogany and alder, how are the two woods put together in the body?

[mhammer]

Many different ways. The "Les Paul" way is to have one wood make up the underside of the instrument, and a second wood make up up the top. I can't quote chapter and verse on the proportions, but let's say the body is typically about 3/4 mahogany and the top 1/4 is maple.

The "BC Rich" way would be to laminate strips of different woods in parallel along the length of the body. This is often done for appearance purposes, but can also be done to lend some strength to the body, or accommodate a through-body neck.

A somewhat different approach is adopted by danelectro, and more recently by Yamaha, where a lighter more resonant (but softer) wood comprises the inner core, and a thin layer of harder wood makes up the top and back.