Sturdy Construction: This umbrella clamp and screws are made of sturdy and durable metal and will securely hold your umbrella. This umbrella holder is easy to assemble and move, and attaches quickly and securely to most patios, balustrades, or railings. The patio umbrella clamp is suitable for umbrella poles up to 4.4 cm thick. The maximum balustrade width should not exceed 6.3 cm. The adjustable boat umbrella clamp offers greater flexibility and is ideal for attaching torches, flagpoles, umbrellas, and other outdoor decorations. Space-Saving: This outdoor umbrella holder is extremely space-saving.