As an alternative to using construction lines during line creation, you can use the X, Y, and Z keyboard modifier keys to lock the corresponding orthogonal axis. This can be useful for additional precision in complex models to control the direction of item construction.
When you are creating in free space, the cursor grids the distance along the locked axis as you move the mouse.
The example below shows the construction line displaying along the X axis, while the mouse cursor is above. The potential line creation result is displayed at an angle of 25.
The example below shows a similar mouse position above the x axis, but holding down the X key has locked the line creation onto the X axis, despite the cursor position being located above the X axis.