Abstract: A drafting or measuring instrument, such as a caliper, divider or compass, has legs pivotally connected at one end and carries working elements at the opposite ends which may be moved between closed and opened positions. A thin case for releasably holding the instrument has an opening with an inner side wall conforming generally to the outer edge of the instrument so that the instrument may be placed in the opening. Formed on the respective opening side wall and the instrument edge are cooperating projections and grooves. The instrument may be manually positioned in the opening with the attaching projections being engaged by the retaining grooves so that the instrument is releasably held in the case until relative pressure is exerted between the instrument and the case to remove the instrument. An aperture may be defined at one end of the opening to receive the working elements of the instrument.