Rail Mounted Bed Side Shelf

The shelf will fit a railing that is around ~17 to ~18 mm wide.   It doesn't require any supports and the length can be easily resized.  The lip is optional and just slips over and is glued on to the mail shelf.  I used 15% adaptive cubic infill and 3 walls.  More strength may be needed depending on what you place on it.  At 15% infill it has no issue holding glass of water and a book.