Please select your home edition
upffront 2018 GFM 728x90

Soft Attachment Blocks - a guide to the basics by

by Phil Anniss 25 Dec 2019 09:00 UTC
Soft Attachment Blocks © Jacques Vapillion / Onefly

There has been a quiet revolution going on with block attachments over the last five years. Soft attachments are universally accepted as the preferred method of securing a block. In this blog we will explain why and then look at some of the basic attachment methods plus some do's and don'ts.

Block Terminology

Let's just establish some basic terminology...

Manufacturers have their own variations but in general, the important elements of a lash block are as follows:

  • Loaded line - the running line which passes around the sheave.
  • Lashing / attachment line - either a fixed lashing or it can be a strop or a soft shackle.
  • Head - Traditionally the load transfer point between the cheeks and the attachment fitting (shackle) however in a lash block it is used to maintain alignment of the block.
  • Cheeks - Traditionally all the block load would pass through the cheeks however in a lash block the cheeks act as a spacer to prevent the lashing line from clamping around the sheave and, working in conjunction with the head, helps block alignment.
  • Sheave - exactly the same as a traditional block
  • Hub / Mouth / Axle - the space at the centre of the sheave through which the lashing line passes, has many different names, depending on manufacturer. The only noteworthy difference between a standard block and a lash block is that the edges are radiused to prevent chafe. It is for this reason that a traditional block cannot generally be adapted to be a soft attachment block.

Why are they different?

The key difference between a traditional block and a lash block is that the attachment line / lashing passes directly through the center of the sheave. In a traditional block, the block cheek plates transfer the load from the sheave to the head of the block to the shackle attachment.

This inherently reduces failure risk of soft attach blocks because:
     a) There are fewer parts involved
     b) Even if the sheave itself failed, the loaded line would still be retained by the attachment lashing line.

Benefits of soft attachments compares to stainless shackles:

  • Lightweight
  • Strong and safe
  • Abrasion resistant
  • Corrosion free
  • Self-align to load which lowers fatigue on block and loaded line
  • Kind to mast, deck and sails with less noise
  • Low maintenance

Do's and Don'ts

Always pass the attachment/lash line through the centre of the sheave:

  • Never just pass the attachment line through the head of the block
  • The cheeks of a lash block are not designed to take the working load of the block

Always ensure the attachment line is constrained at the head:

  • There are two general types of soft attach block head - where the lash line passes through a central hole in the block head or where small lashing holes are provided to secure the attachment line with sailing twine.
  • If the attachment line is not constrained the block can capsize.

Always ensure that the lashing/attachment line is secured to a point with radiused edges:

  • E.g. Do not attach to cut metal eyestraps with sharp edges

More turns of a smaller diameter lash line generally provides a neater finish and is more easy to securely knot

Remember the break strength of a lash line is generally limited by the knot or splice, therefore the break strength of the lashing line needs to be considerably more than the break strength of the block

Use a secure knot:

  • e.g. Carrick /Zeppelin/Hunters Bend
  • Do not use a Reef / Granny / Square knot which can easily work its way lose
  • Check out Animated Knots for more information on secure knots


One of the real attractions with soft attachment blocks is that they are so flexible in terms of application. Whilst it does take some time to get used to the different possible configurations, all the main manufacturers provide some good guides on techniques to get the most out of your lash blocks.

If you have any questions please do not hesitate to Contact us using our contact form or fill in the running rigging enquiry form.

Related Articles

Join on the Foredeck
Get a free 50 Euro voucher when you join this exclusive club With the launch of the all-new website we are also pleased to present the Foredeck Club, exclusively for boat owners who are serious about their sailing. Posted on 1 Apr
Andersen Winch
Laser focus on a simple, reliable, high-quality design As part of the Ronstan brand, Andersen are 100% focused on providing simple, reliable high quality sailing winches. Anderson made the decision early on to focus on one standard range and do it well. Posted on 26 Mar
Adding a Bowsprit 'Turbo Charge'
What is the Facnor Bowsprit? Facnor is a specialist in designing and manufacturing furling systems, and therefore it should come as no surprise that they have a retrofit bowsprit solution. Posted on 18 Mar
What's so special about the Ronstan Orbit Range?
An in-depth look from Well known around the world, Ronstan is a great choice for blocks and sheaves for a variety of sailors. They have developed a number of ranges from the basic Utility range to the advanced precision Orbit range. Posted on 12 Mar
Can Upffront become sailing's
Andy Rice interviews managing director Phil Anniss Upffront has created a few ripples in the marine industry since the company launched in 2015. However, the online supplier of performance hardware and rigging systems is looking to make much bigger waves in 2020. Posted on 4 Mar
Gotifreddi Maffioli cruising lines explained
A vast range of very specialist cores and covers Family run, Italian rope makers, Gottifredi Maffioli, have an international reputation as one of the leading brands across the full spectrum of yachting lines from Olympic class dinghies, grand-prix TP52s and mini-maxis to the largest superyachts. Posted on 27 Feb
Karver's double whammy at the DAME Awards
Compact winch and carbon handle applauded in Amsterdam The Dame Awards are the leisure marine industry's equivalent to the Oscars, awarded every year at the Marine Equipment Trade Show (METS), held in Amsterdam each November. Posted on 19 Feb
Local Ropemaker to America's Cup Supplier
How did little Italian rope producer Armare make it to the top? Despite being a small, family-run business, Armare Ropes are operating at the top of their game. Posted on 13 Feb
Robline Rope Cruising Ranges Explained
How to choose which range you need The success of Robline as an international rope brand is based on decades of expertise in manufacturing fibre ropes, the experience of professional sailors in the company, and the intensive collaboration with Olympic gold medallists. Posted on 5 Feb
nke Depth and Speed sensors explained
nke are the standard for the majority of Mini-Transat and IMOCA 60 classes The marine industry has been awash with new and exciting technological innovations in recent years and standing at the forefront are companies like nke marine electronics. Posted on 30 Jan
MBW newsletters (top)