An adjustable gullet plate with interchangeable, adjustable portions and joints which are connected and secured to one another using interlocking elements and fasteners. The adjustable gullet plate may include interlocking elements equally spaced at or at about known increments and terminal portions connected successively to create points of adjustment. The gullet plate may be adjusted into an asymmetric configuration to fit a horse with an asymmetric body shape. The adjustable gullet plate can be installed in a saddle and then be adjusted to fit a horse's body shape by accessing at least one fastener securing an adjustable joint, loosening the fastener to disengage interlocking elements to permit radial movement, adjusting the radial displacement and interior angle of at least one adjustable portion to fit a horse's body shape, and tightening the fastener to reengage the interlocking elements and prevent further radial movement.