The fitted sheet is half done. The angle at the left is the top of the sheet. The relatively straight seam across the bottom is a corner seam. The angle to the right is where the sheet snugs under the mattress:
I have yet to serge the raw edges to the right and apply elastic all around -- and, make the top sheet.
There's a message on my phone from the library to tell me that some reserved books have come in. I'm going to take a short sewing break by finishing the book I'm reading - "Second Chance Pass: by Robyn Carr.