This is a must-have form and you will need one for each different sized instrument. It is used to basically construct the entire body of the guitar or ukulele and trim it out as well. Use this form to hold bent sides, glue head and tail blocks, glue linings, glue top and back plates, rout purfling and binding channels and more.
Inside Forms are intended to keep the instrument in perfect shape and registration with parallel sides. When used in conjunction with Spreader Jacks, the instrument can be made to exacting standards.
At the luthier's option, attachment screws can be placed at the top perimeter of the form, allowing attachment of rubber bands or elastic straps for attachment of top and back plates and bindings.
The inside form can be opened by simply removing the screws on the underside of the floor of the form. Some luthiers also choose to include a "gate" to the form to allow the instrument to be held in the form when the neck is attached.
For Acoustic Guitars, the Form Package consists of 3 sheets of drawings showing the plan and elevations of the inside form, the workboard plan and Heated Side Bender form insert for the selected guitar shape.
Ukulele Plan Form Packages consist of 2 sheets of drawings detailing the inside form and so not include a workboard plan.