When drywall panels are installed in a building, and the seams taped, prior to painting the wall surface, there is often applied a spray texture, which is followed by painting.  The spray texture will provide a desirable background pattern, and also obscure some of the seams that might appear in the drywall surface. 
There are in the prior art various spray texturing tools or devices which utilize pressurized air to spray the texture material onto the wall surface.  Some of these use compressed air as the gaseous medium to spray the textured material, with the pressurized air being derived from a remote source that feeds the air through a hose to the tool.  There are also tools which are totally handheld, with the pressurized air being produced by manually reciprocating the piston of an airpump that is built into the tool. 
When an existing drywall surface is being repaired, quite often a small section of drywall will be removed and another piece of drywall put in its place.  The seams of this piece of drywall must then be taped, and (if the surrounding surface is textured) then have a texture surface treatment that would make it match with the surrounding drywall surface.  It is, of course, desirable to have the spray pattern on the patch match that of the surrounding surface. 
Also, when a rather small "patch" of drywall is to be spray textured, there is the matter of convenience.  One approach has been simply to provide the spray texture material in an aerosol can, and the textured material is dispensed directly from the can to be sprayed onto the drywall surface.  However, one of the considerations is how this can be accomplished in a manner to provide proper matching of the texture with that which is on the surrounding drywall. 
U.S. Pat No.  5,037,011 (Woods) discloses such an aerosol texture spraying device where the spray texture material is dispensed directly from the nozzle of the aerosol can.  In a commercial embodiment of a device such as this, when there is higher pressure in the container, there is a relatively fine spray pattern.  For a more coarse pattern (i.e. with larger particle sizes), the can is inverted and the nozzle depressed to dispense a certain amount of the propellant gas for a few seconds.  Then the can is turned upright and the spray texture material dispensed at a lower pressure to provide the spray pattern with larger particle sizes.