Abstract: A construction set of resiliently flexible pipe incorporating an integrally formed interlocking pipe joint. The set and joint are adaptable for use on a small scale as a toy and on a larger scale for construction of furniture, geodesic domes, and the like. Outwardly bowed longitudinal members integrally formed in the pipes are adapted to be inserted with the members of one pipe interlocked with the members of the other pipe. In alternate embodiments, a spherical member or hardenable material are inserted within the assembled joint.

Abstract: A musical instrument for producing slapping sounds occurring at an audibly distinct asynchronous rate. A rigid slat member has a plurality of flexible slat members disposed adjacent thereto on at least one side and connected at one end to form a gripping handle. The flexible slats are increasingly weighted away from the rigid slat member such that when the rigid slat is rapidly accelerated through a swinging motion by gripping the handle the outermost slats will be flexed a greater distance than the inner slats. Consequently, the time for unflexing when the swinging has stopped is greater for the outer flexible slats whereby they strike in a slapping motion at a sufficiently delayed time to be audibly distinguishable.

Abstract: An ink composition for writing instruments having a porous writing point, which will write satisfactorily on relatively smooth, hard surfaces (e.g. solid plastic surfaces) and which can easily be erased from said smooth, hard surfaces by merely wiping with a dry cloth or paper tissue. The ink composition contains, as essential ingredients, water, a water soluble dye, a silicone surfactant, and a release agent in which the water soluble dye is insoluble. The ink composition may also contain a wax to prevent dusting. An erasing system including a marking board having a smooth, hard, non-porous surface of plastic and a porous point pen having an ink therein which will deposit uniform, legible traces, markings or lines on said plastic surface and which can be removed therefrom with a dry cloth or paper tissue.