You can just create an SKU called “miscellaneous” or “misc”, leave the description blank and price zero. When you sell the SKU, the system will ask description and price on the fly.
To create an SKU at POS front end when selling, type CREATESKU in the code box where you scan the barcode.
If you do special order or custom work, you can use SPECIALSKU
You can also create an SKU starting with the word AUTOSKU. When you complete the transaction, the system will automatically create a new SKU using AUTOSKU as a template. This is the same as SPECIALSKU, but it will not force you to complete the transaction as a special order.