Sketching is the primary input used to create the various items in your design project.
Strokes can be sketched and erased easily allowing you to quickly get your design concepts underway.
It is best if strokes overlap at the corners, however, strokes that almost intersect also work fine too.
If you want your strokes to clean-up to neat horizontal and vertical strokes use the Drawing Settings.
Using the Edit Toolbar you can switch between the Pencil and the Eraser to determine your current mode.
If you have Apple Pencil 2, you can use the pencil tap double-tap to quickly change from Pencil to Eraser and vice versa.
However, with Pencil mode selected you can also use a squiggle to quickly erase strokes:
When erasing strokes with a squiggle, these are automatically trimmed to the nearest two intersecting strokes.
If you want to clean up all your strokes you can double-tap the Eraser button.