Building a piece in parallel through a point

This mode is intended for creation of the linear object, located in parallel to chosen piece of the metrics and passing through the specified point. The created line is equal by length to a piece of the metrics of source object. It is necessary for user to specify a piece of the metrics of linear or area object on a map, in parallel to which he is going to construct a new line.  

For this purpose it is necessary to choose source object of a map, thus the cursor should be placed in area of the piece of the metrics necessary to us. In other words, that piece of the metrics which is the nearest to the cursor of the mouse, and will be used as a source piece. After a choice of a source object specify dot object through which a created piece should pass.