Purchase Luck item ticket and click on the "Use" button

Go to Elbeland and find out David

Talk to David and click on the "Exchange" button

Put Lucky Item Ticket and click on the combination button

Click on the "Refine Lucky Item" button

Put any items in order to create Jewel of Extension

Click the on combination button

Obtain Jewel of Extension at certain rate

This process can be failed at a certain rate
Jewel of Extension is used for increasing durability of Lucky items
Put Jewel of Extension of the items you want to fix