The process section on the bottom of the Assembly Order layout contains 4 options:
Start Assembly - This changes the quantity value for the item being built as well as the BOM line items. The quantity for the item to be assembled is moved from On Backorder to On Order. The quantity for the BOM items is moved from Available to Allocated.
Complete Assembly - The completed assembly must be received. If a new Receipt record is available, it will be added as a line. Otherwise, a new Receipt record will be created.
Print Preview - This creates a PDF document.
Cancel - Cancels the Assembly Order. This can only occur when the Assembly Order status is New or Started. The quantity values are re-set for both the item to be assembled as well as the BOM items. Transaction records are created.