Completely exclude items from the sorting logic using the 'items' option

• Item 1
• (I'm not sortable)
• (I'm not sortable)
• Item 4
• Item 5

Keep the items as valid targets, but non-draggable, using the 'cancel' option

• Item 1
• (I'm not sortable)
• (I'm not sortable)
• Item 4
• Item 5