A portable work screen apparatus including a semi-rigid screen and at least two supports, each having an attachment device, the attachment device having a magnet for, in use, releasably connecting the screen to a surface proximal to a workpiece, wherein the at least two supports are spaced apart, such that, in use, the screen is extending therebetween and is flexed to a desired configuration. Gate dielectrics of equal thickness are provided to a first and second transistor on the semiconductor substrate. The hard coating has a composition represented by the formula TixAlyMzN, in which the \u201cx\u201d, \u201cy\u201d, and \u201cz\u201d respectively represent the atomic percentage of Ti, Al, and M. When one or more hooks engage the chain of the chainwheel, a further feature enables the tool to lock down on those engaged chains, and, thereby, provide safer pulling and pushing to open and close the chain-operated assembly. At least one selected from the free layer and the pinned layer includes a synthetic antiferromagnetic structure formed of a first ferromagnetic layer, a second ferromagnetic layer, and a ruthenium-rhodium alloy layer provided between the first and second ferromagnetic layers. A back flow preventor may be included to cooperate with the clean air hose to prevent a back flow of crankcase fumes through the clean air hose.