Abstract: A non-slip screw of the type having a threaded shank and a slotted head, including a locking surface defined in the screw head by a central transverse slot which extends across the top of the head for engagement with a screwdriver blade tip. The locking surface includes a pair of radially outwardly extending inclined walls extending downwardly from each end of the transverse slot. An especial screwdriver having its exterior blade tip configured complementally with the pairs of radially outwardly extending inclined walls is engageable with the locking surface, so as to rotate the screw head in either direction. The screw head is characterized by its positive grip with the screwdriver blade tip, notwithstanding actual screwdriving or unscrewing and removal of the screw.

Abstract: A single cycle, rotary combustion engine having constant fuel feeding. A circular housing defines an annular chamber through which a complementally curved pistonhead travels and works only upon the explosive or combustion stroke. A drive shaft is supported transversely of the housing, such that a piston rod extends radially from the drive shaft through an inner sealing drum so as to present the curved pistonhead within the annular chamber. Fuel and air are fed through the piston rod within the annular chamber via one or more ports in the trailing edge of the pistonhead. An ignition point and an expulsion port, mounted approximately 280.degree. from each other are sealed from one another by rotary means. The engine is characterized by its elimination of valves and reciprocating parts.