Abstract: A gun lock utilizes an internal combination wheel which is advanced by the pressing of combination buttons which urge a combination wheel toward an unlock position. The unlocking of the gun lock enables a spring loaded rachet to be springingly urged quickly out of engagement with a main housing of the gun lock to enable the gun to be readily fired. The combination is set by the orientation and radial positioning of a series of angled blocks supported by the combination wheel. The combination setting for each advanced position of the wheel is based upon the combination wheel's position resulting from the prior movement in executing the previous combination number.

Abstract: A clean room ceiling having an air impervious filter support and air flow path-defining filters supported by the support, and a permanently fluid, nonevaporative non-air-flow-displaceable gel blocking air flow past the support except along the filter defined air path.