For a <Line segment> setting one should press the button. Then, in any consequence, select elements, which will determine the line. If there are several possible variants of Line setting, the system will reflect these variants and will wait for the right variant choice or, in case of need, enter appropriate parameter in the parameter panel.
There is some examples of point definition below.
Environment of 2D geometrical constructions
By two mouse clicks
From one snap point to another snap point
From the snap point at the required angle to position determined by the mouse click
From the snap point at the required angle to the required distance
From the snap point under required angle to the snap point
Line construction in parallel to the required line on the required distance
Parallel line construction tangential by curve
From the snap point of in parallel another line with required distance
From the snap point in parallel another line to the snap point
From the snap point in perpendicular another line
Tangential by curve and perpendicular to line
Tangential by curve from snap point
Tangential from two curves