Square Button

The square button has multiple features. It's located on the side (on the left side if you are using Right Hand Layout or on the right side if your layout is set to Left Hand). 

Draw a straight line

Tap and hold the square button while drawing to create a straight line.

Move in a straight line

Finally, you can also move a selection in a straight line by holding down a square as you move a selected stroke with your apple pencil (all features work in both camera modes).

Multiselect function

Select multiple strokes by holding down the square in selection mode and use your other hand to make your selection.                                                              

Edit selection

You can also transform a selection by selecting a stroke, holding down the square button with one hand, and then using your other hand to complete finger gesture movements (two-finger pinch, rotate and pan, as well as one-finger movement). This will resize, rotate, move or orbit your selection only.