A ferrule of a beach umbrella is a protective metal or plastic the cap that fits over the top of the shaft that sticks out above the canopy of the umbrella. Ferrules protect the end of the shaft and also help keep the canopy in place. Some ferrules are threaded and screw down over the shaft. Other types of ferrules are attached with a screw or simply fit snugly over the end with no other fastening mechanism except friction. The ferrule of an umbrella may wear out over time and need to be replaced.
Contact the manufacturer of your beach umbrella and buy a replacement ferrule.
Lay the umbrella on the ground in the closed position. Inspect the ferrule and figure out how it is attached to the shaft.
Pull the top end of the umbrella off the ground using one hand. It may help to support it on the edge of a sturdy table or over a sawhorse.
Grasp the ferrule with the other hand and, if it is a threaded type, turn it counterclockwise to remove it. Use pliers if you cannot loosen it using only your hand. If the ferrule attaches to the shaft by a screw, use a screwdriver to unscrew it. Your beach umbrella's ferrule may also be attached with hardware that needs another kind of tool such as a hex wrench. Use whatever is appropriate.
Apply a bit of spray lubricant around the threaded ferrule if it does not easily turn. For screwed-in types, spray the end of the screw with the lubricant. Let the lubricant work for about a minute then try to remove the ferrule again.
Position the new replacement ferrule over the end of the shaft where the old one sat. Turn threaded types clockwise. For screw types, attach them using a screw or other hardware as appropriate.
Read the manufacturer's instructions for the type of beach umbrella you have in case there are unusual directions or specific details about the ferrule's attachment. If you cannot locate instructions for your umbrella, try contacting the retail outlet where you bought it. They might have replacement ferrules or know a place where you can find them.