If this command is enabled, you can snap on the entity when you create 2D entities: line, arc, spline and so on.

1.

Enable Tools > Sketch Options > Snap On Entity (Default of this is enable).

2.

Click Tools > Sketch Entities > Line to create a line. Move mouse on a line to find middle position of line. When you can see  icon, click start point of a line.

3.

Click an end point, when you can see  icon.

4.

Click OK to finish creating a line.

Note

You can directly access Snap On Entities command on the pop up menu when you click the right mouse button on the blank area in the sketch mode.