If you sell gift cards through the webstore the sale process may not be immediately obvious, though it's pretty simple!
Note: This write-up will not explain how to fulfill webstore orders. This will only explain how to to load a gift card before scanning it out to fulfill the web order.
As an example we'll pretend we're selling a $10 gift card on the webstore.
1) Pull up the desired gift card listing and change the quantity to -1 to refund the cost.
Refunding the item will ask if the item is re-sellable. Click "yes." This will add one copy of the item to the store's inventory.
Bring up the same gift card listing once again. The POS will automatically apply the pending credit from the return transaction to the price of the new card.
Once the gift card is loaded, you're ready to fulfill the web order! It is recommended that for ease of scanning you print out labels for your gift card listings, however a search and copy of the listing's UPC code will produce the same result. Once the web order has been scanned out the gift card will be removed from inventory, so by the end of the process of fulfilling the web order you have zero inventory change.