Building a custom box to ship a guitar is relatively simple. However, care must taken to prepare and do it properly to ensure the safe transport of your instrument. Materials can vary, but cost of shipping must be taken into consideration when choosing the components to your crate. Ideally, you should ship your guitar in its own case for added protection. If you do not have a case for the guitar, building a custom box is still a good choice for safe shipping.
Lay out the foam insulation for bottom encasement. Place two pieces side by side if necessary to make sure it is wide enough to hold a guitar that is laying flat.
Glue the two pieces together if extra width is necessary to hold the guitar, and allow glue to dry.
Mark out a rectangle in the foam that allows for about 5 cm (2 inches) on either side of the widest point on the body, using the guitar as a guide. You will need the permanent pen for marking and the metre rule for measuring and a straight edge.
Cut out the rectangle with the handsaw.
Repeat the process for the upper foam encasement using the bottom foam as the template.
Lay the guitar on the bottom encasement and trace around it as accurately as possible with the permanent marker. Repeat for the upper encasement.
Scoop out the foam to a 2.5 to 2.7 cm (1 to 1 1/2 inch) depth from the upper and lower foam rectangles using the carving knife and spoon.
Lay the cardboard out flat and place the foam encasement in the centre.
Wrap the cardboard carefully around the encasement, taking care to completely cover the foam core.
Cut off any excess cardboard using the box cutters or industrial scissors.
Place the guitar in the foam protection, and wrap the cardboard around the foam and secure it with strapping tape at all corners and seams.
There is no such thing as too much tape when shipping something as important as a guitar. For added protection, you can use plywood instead of cardboard. However, this is expensive and adds dramatically to weight, which increases shipping costs. Most guitar retailers have boxes and foam cores they are willing to give to those who ask. They receive their guitars this way and you can often skip building your own by simply asking for one from a shop.
Always insure the guitar you are shipping for the full retail value of the instrument. Accidents can still happen no matter how carefully it is packaged.