The Draw tool works in several different ways depending on the the subtool that is selected.
The Line subtool draws a single segment constrained to be a straight line.
To Draw a Line
To Draw a Line Segment
Position the cursor where you want the segment to begin. Press the left mouse button to anchor the initial node. Drag the mouse and the line will follow from the initial node. Release the mouse to drop and anchor the end node.
Note: There are no snapping rules for drawing applique blocks. If you want to apply snapping, you can. There are several snapping options available in the Precision Bar.