Selecting Slugs, Slides & Shackles

Item # X-HT-300031

Slugs, slides and shackles are useful little pieces of hardware that make raising and lowering a mainsail a breeze. If only putting them on the sail were as easy. With a wide array of options and pairings it can be daunting trying to decide if you need a slug or a slide let alone decide what size to use and how to attach it. This post is designed to take out a bit of the guesswork so you can work your mainsail with confidence.

A selection of slugs, slides and shackles

Why Use Slugs or Slides?

Why bother with slugs and slides at all? Well, there are some great perks for taking the time to install these on your sail. The main benefit is that they make for easy operation of your mainsail. Utilizing slugs and slides lets the sail move easily inside the track and, when used with a sail stop, the slugs and slides allow the sail to quickly and easily stack on the boom in the mast slot. This prevents the sail from coming out the bottom of the mast slot and catching the wind, creating havoc. Additionally, slugs and slides reduce the wear on your sail by keeping it out of the mast slot.

What are Slides, Slugs and Shackles?

In order to choose the best fitting slugs or slides for your mainsail, let’s first go over some terminology.


Small nylon barrel that is secured ahead of the boltrope and inserted into the slot on the mainsail instead of the rope. Slug diameters range from 5/16 inch to 1/2 inch.


Small flat “T” shape piece that is secured ahead of the boltrope and inserted into the slot on the mainsail. Flat slides range from 5/8 inch to 7/8 inch wide.

Internal Slide

A slide that fits inside the mast slot. This is the most common type of slide.

External Slide

A slide that fits into a track that is mounted on the mast. These slides were common in the days of wooden masts when internal slots were difficult to create.


Secure around the bail of a slug or slide and attach to the sail. Most shackles attach to the sail via a spur grommet, although some attach right through the sail via self-tapping screws.

Which to Choose?

The choice really boils down to fit and personal preference. First and foremost, you want to make sure that the slugs and slides properly fit your mast slot. Then select a shackle that fits through the slug or slide. If you are replacing old hardware match the slugs and shackles to the old ones, either using the same parts or new parts with identical dimensions. If you can’t find an exact match for existing parts, then replace them all. Sails won’t function properly if the hardware has different amounts of space between it and the sail.

If installing slugs or slides on a new sail, start by measuring the sail slot. Pick a slide or slug that will fit well inside the slot with some wiggle room (think not too tight, not too loose). Slides are designed to fit in rectangular slots and slugs are made for round slots.

If the sail has full battens, we recommend using AllSlip or Ronstan slugs. These slugs are all nylon and are specially designed to help distribute the batten pressure to prevent jamming when hoisting or dousing a full batten sail. The Ronstan slugs even have rolling ball bearings in the bottom to keep them sliding on the mast.

Sailrite stocks a full selection of slugs and slides. Take a look at the options to find a good fit for your sail.

How to Install

With slugs or slides chosen, now it is time for installation. Depending on your preference and your sail, there are several different options to choose from. The most common way to attach a slug or slide is by using a shackle. Shackles should all be the same length and should be wide enough to fit around the boltrope and deep enough to bolt through a grommet (if installed). Shackles come in plastic or metal varieties that either snap or screw into place.

The strongest installation method is using a shackle and grommet. In this method, the slug hangs from the shackle, which is secured to the sail through either a #1 or #2 grommet. Grommets provide strong attachment points and work with both metal and plastic shackles. If grommets don’t appeal, there are also Screw-On Plastic Shackles. These shackles have a screw that taps right through the sail to secure it but are only suitable for use on smaller boats.

Or, there is always the option to scrap the shackle altogether and use webbing instead. Create a webbing loop to secure the slug and either sew the loop directly to the sail or loop it through a grommet. Installing slugs with webbing is the most labor-intensive method, but does provide the most give and take for the sail.

Here are some attachment examples:

Diagram of different attachment methods for slugs and slides

Choosing the right shackle for your slug or slide can be difficult with so many types and sizes to choose from. We’ve put together a handy guide to aid in the process. This Slugs, Slides, and Shackles PDF matches slides and slugs to which shackles will support them on a standard 5/16-inch boltrope with a #2 spur grommet.

In the end, sorting through all the options is worth it. Finding a great fitting slide, slug and shackle system will give you the smoothest running mainsail on the water.

For more information on slugs, slides, and shackles check out this video series.