Ronstan Series 40 Upright Lead Sailing Block

The Ronstan Series 40 Upright Lead Sailing Block is made for low-profile line routing, particularly where a halyard needs to turn at the mast base toward a clutch, jammer, or cleat. Its upright lead keeps the rope close to the mounting surface and makes a controlled change of direction without adding the height of a hanging swivel block. That layout is useful on compact decks where several halyards and control lines converge near the mast. It also makes replacement straightforward when the existing system already uses a fixed mast-base lead.

Ronstan uses a UV-stabilized Acetal sheave for smooth, low-maintenance rotation around a stainless load housing. The fixed housing supports the sheave directly and keeps the line path stable as the halyard is tensioned. Because there is no swivel head to correct a poor approach angle, the mounting position matters more than it would with an articulating block. A clean installation should let the rope enter and leave without pressing hard against either side of the sheave.

• Low-profile upright lead for mast-base routing
• UV-stabilized Acetal sheave
• Stainless load housing for marine durability
• Fixed line path suits halyards and similar controls

Position the block so the halyard turns naturally toward the next piece of deck hardware and does not rub the mounting surface. Check the fasteners and backing structure for the working load of the complete system, not just the block itself. Regular rinsing is usually all the sheave needs, but the rope groove should still be checked for wear when the halyard is serviced. For more mast-base leads and sailboat control hardware, browse more Sailing Hardware.