1. A device used by an observer to estimate the distance between said observer and a designated object, comprising: a planar surface marked with reference point markings, said reference point markings including a single main mark located on said planar surface, and a plurality of reference point markings, said plurality of reference point markings including corresponding numerical marks associated with said reference point markings, wherein a distance between each of said plurality of reference point markings and said single main mark has been determined prior to the construction of the device, said reference point markings and said single main mark providing corresponding dimensions with respect to said observer's eye-to-eye so as to allow estimation of said distance between said observer and said designated object using a parallax effect when said device is held between said observer's eyes and said designated object, and a solid housing or grip which said observer may use to hold the device during its operation.