Abstract: A device for holding a flexible bag open for filling. The device includes a generally triangular insert that, when folded at two corners, is able to stand upright for facilitating placement of a flexible bag over the upright corner of the triangular insert, and which may thereafter be placed with the flat face down on the ground to facilitate the raking of leaves therein, and one or more reinforcing members on the insert providing a springlike action to the folded corners and keeping the bag open.

Abstract: A one-man field survey instrument for conducting small scale engineering surveys. The instrument automatically measures relative vertical and horizontal angles as it is moved over the terrain. The measurements are thereafter processed to prepare a topographical survey. Alternative configurations are disclosed as are methods for using the instrument.

Abstract: An arming device is interposed in the electrical circuit between the electrical switch at a control site and a remote explosive. The arming device is physically located near the explosive and is connected by a fluid pressure line to a pressure source at the control site. Until such time as the arming device is activated, the danger of premature detonation of the explosive from current induced in the conductor between the explosive and the switch is eliminated, and the fluid-pressure controlled arming device is not susceptible to such induced current. Both piston and diaphragm-type arming devices are disclosed.