Is there a way in Sketch to expand a shape? For example, let's say I have an outline of something. I'd like to expand that outline to be a solid shape so I can apply boolean operations to it with other shapes. Is that possible?
EDIT for Sketch 3.6.1
Choose Layer > Convert to Outlines.
Strokes cannot be expanded (currently, v2.4.3). Edit: You can choose vectorize stroke in Layer (or Edit for older version) > Paths > Vectorize Stroke
However, you could create the shape and then use a mask to make the diagonal cut. In the example I have made the mask visible in red (normally this would not be shown).
You can create a mask by drawing a single shape (can be constructed using boolean shapes). Then select 'Use as Mask' when ctrl-clicking the layer in the layer pane. Make sure you position the layer right below the layer you want to mask (in the layer pane).