Ronstan Series 40 Single Cheek Sailing Block

The Ronstan Series 40 Single Cheek Sailing Block is a low-profile turning block for mainsheets, halyards, vangs, and other control lines that need to stay close to a deck, mast, or boom. Mounting the block directly against a surface reduces stack height compared with a hanging swivel block. Ronstan also notes that a curved-surface adapter can be used on a spar, and compatible cheek blocks can be stacked where the application calls for a double arrangement. That makes the block useful for refits as well as new line-routing layouts on small sailboats.

The sheave is molded from UV-stabilized Acetal, a self-lubricating material chosen for low maintenance in a wet environment. Fiber-reinforced nylon cheeks protect the sheave from impact while keeping the block light, and stainless hardware carries the primary load. The fixed cheek format removes unnecessary articulation when the line direction is already known. It also leaves the rope path easy to inspect because the sheave sits close to the mounting surface instead of moving around a shackle head.

• Low-profile cheek mounting for fixed line turns
• Self-lubricating UV-stabilized Acetal sheave
• Fiber-reinforced nylon cheeks
• Can be used with a curved-surface adapter where appropriate

Set the mounting angle carefully so the rope runs through the center of the sheave across the full working range. If the block is stacked or fitted to a curved spar, follow Ronstan's load and adapter guidance for that configuration. Inspect the mounting fasteners and rope groove during normal rigging maintenance, especially where the line changes direction sharply. For additional fixed turning blocks and spar-mounted rigging, browse more Sailing Hardware.