Rigging Blocks: Types, Uses and How to Choose

What Are Rigging Blocks?

A rigging block is a pulley assembly used to redirect a rope, wire rope, or synthetic line, or to create a mechanical advantage that reduces the force required to lift or pull a load. Blocks are used in overhead lifting, marine operations, construction hoisting, and off-road recovery. The block housing contains one or more sheaves, grooved wheels over which the rope runs. The block attaches to a fixed anchor point, crane hook, or load via a shackle or swivel.

Rigging blocks are one of the oldest mechanical tools in lifting and rigging. They remain essential wherever the direction of a pull needs to be changed, where the available pulling force is less than the load weight, or where a long reach pull needs to be redirected around an obstacle. For a full overview of hardware used alongside blocks in rigging assemblies, see our guide to 5 Most Common Types of Rigging Hardware.

How Rigging Blocks Work

A single block changes the direction of the rope without providing mechanical advantage, the same pulling force is required, but the operator can pull in a more convenient direction. When multiple blocks are used together in a tackle arrangement, they multiply the mechanical advantage and reduce the required pulling force.

A two-part line arrangement, one fixed block and one traveling block with the rope running between them, reduces the required pulling force by approximately half. Each additional part of the line further reduces the required force but also increases the length of rope that must be pulled to move the load a given distance. This trade-off between force reduction and rope travel is the fundamental design consideration in block and tackle selection.

For a broader overview of rigging methods and when to use each, see our guide: Mastering Rigging Techniques: Choosing the Right Approach for Your Applications.

Types of Rigging Blocks

Snatch Blocks

Snatch Blocks have an opening side plate that allows the rope or wire rope to be inserted without threading it through from the end. This makes snatch blocks the most versatile option for field rigging, recovery operations, and applications where the line is already under load or where threading from the end is impractical. The side plate opens to accept the rope and closes and locks securely before the load is applied.

Snatch blocks are available with hook or shackle attachment at the top, and in single or double sheave configurations. They are the standard block type for construction, off-road recovery, and general field rigging where the rope needs to be installed quickly and in-the-field. Holloway Houston stocks snatch blocks from Crosby, Van Beest Green Pin, and Skookum in a range of WLL ratings and rope sizes.

Fixed Blocks

Fixed blocks have a closed housing with no opening side plate. The rope must be threaded through from the end during the initial rigging setup. Fixed blocks are used in permanent or semi-permanent tackle arrangements where the rope is installed once, and the block remains in service, such as in crane boom tip assemblies, material hoists, and fixed tackle systems in marine and industrial environments. Fixed blocks are structurally stronger and more rigid than snatch blocks at equivalent load ratings.

Swivel Blocks

Swivel Blocks incorporate a swiveling attachment at the anchor or crane hook end that allows the block body to rotate relative to its attachment point. This prevents the block from binding or side-loading when the rope angle changes during a lift or pull. Swivel blocks are used where the direction of pull shifts during operation in marine applications, on swing cranes, and in recovery operations where the vehicle being pulled changes direction relative to the anchor block.

Sheaves

Individual Sheaves are the grooved wheel components inside a block. They are also used as standalone components in custom block and tackle assemblies, in crane boom tips, and in fairleads where a rope or wire rope needs to be guided around a fixed radius. Sheave selection requires matching the groove profile diameter to the rope diameter, an undersized groove concentrates stress on the rope at the contact point, reducing rope life and load capacity. The sheave material and bearing type must also be suited to the application load and operating speed.

Selecting the Right Rigging Block

Block selection requires knowing the maximum line pull the block will carry at its attachment point, not just the load weight. In a tackle arrangement, the block at the anchor carries more force than the load weight because it supports multiple parts of the line. The block WLL must be rated for this total anchor load.

• WLL : The block attachment WLL must cover the total anchor load including all rope parts.
• Rope type and diameter : Sheave groove must match the rope size and construction.
• Attachment type: Shackle mount for permanent rigging, hook mount for quick connection and release.
• Side plate : Snatch block for field use, fixed block for permanent installations.
• Number of sheaves : Single sheave for direction change, double or more for mechanical advantage.
• Environment : Stainless or galvanized sheaves and housing for marine and offshore use.

Browse our full range of Rigging Hardware for blocks, shackles, and associated hardware.

Inspection

Inspect rigging blocks before each use. Check the sheave for wear, flat spots, cracking, and free rotation, a sheave that does not rotate freely will abrade the rope at the contact point and cause premature rope failure. Check the side plate of snatch blocks for secure closure and locking. Inspect the attachment hardware (shackle or hook) per ASME B30.26. Check the block housing and cheeks for cracks and deformation. Remove from service when WLL markings are illegible or when any structural component shows damage that could affect load-carrying capacity.

Wire rope running through blocks is inspected per ASME B30.9 at the points where it contacts the sheave groove, as this is where wire fatigue and abrasion concentrate. Blocks with worn sheave grooves accelerate rope wear and should be refurbished or replaced. See also: Wire Rope Clips for wire rope termination and end connection hardware.

For professional rigging inspection and certification services, visit our Rigging Inspection Services page.

Contact Holloway Houston

Holloway Houston stocks snatch blocks, fixed blocks, and swivel blocks from Crosby, Van Beest Green Pin, and Skookum. Browse our full Rigging Hardware