Double Slider

Definition and Overview

A double slider zipper is a zipper with two sliders threaded onto the same set of teeth or coil chain. By changing the position of the two sliders, the opening can be opened from the top or from the center, improving ease of use while worn or when stored.

“Double-ended opening” is a common way to refer to a double slider, but it may also be used to indicate the opening style. In purchase orders and specifications, it is important to clearly state the slider orientation and whether an opening device is included.

Structure and Opening Method

A zipper consists of interlocking teeth, zipper tape that holds the teeth, a slider that opens and closes it, and top and bottom stops that secure the ends. In a double slider, in addition to these parts, the orientation of the two sliders and their stopping positions affect how it functions.

In a head-to-head arrangement, where the two sliders’ pulls face each other, and in a tail-to-tail arrangement, where they face opposite directions, the opening position and appearance differ. In an open-end specification where the bottom end separates, an opening device may be used, and it may be used as a two way separator specification that opens from the top and bottom.

• Head-to-head: an arrangement in which the pull sides of the two sliders face each other.
• Tail-to-tail: an arrangement in which the pull sides of the two sliders face opposite directions.
• Two way separator: mainly for open-end zippers, a specification that can be opened and closed from either the top or bottom side.

Types and Specification Checks

Double sliders vary depending on the type of teeth, such as metal, plastic, or coil, the teeth size, the tape material and color, and the slider shape. The overall zipper specification is selected according to fabric thickness, required strength, and applications.

Length is generally checked by the effective length from the top stop to the bottom stop on the closed zipper. However, because the standard may differ depending on whether an opening device is included and on the stop design, confirm it using the specification sheet, actual sample, and the manufacturer’s size notation.

• Teeth size and type
• Zipper length and excess at the tape ends
• Open-end or closed-end type
• Slider orientation, pull shape, and whether a locking mechanism is included
• Specifications for the top stop, bottom stop, and opening device

Main Applications

For front openings in outerwear and coats, it is used to create room at the hem when sitting and to secure range of motion when walking. In garments worn in layers, the opening at the lower side can also make it easier to adjust the temperature inside the garment.

In bags, boxes, bedding covers, and interior applications, it can be opened only in the center to remove or insert contents, or to adjust the opening range. The longer the opening, the more important it is to consider the slider movement direction and operating position for the intended application.

Selection and Sewing Notes

Because there are two sliders, before sewing, move both sliders to the specified position and check the opening direction. By sewing while keeping the left and right tapes untwisted and maintaining a fixed distance from the teeth end, it is easier to reduce tape waviness and slider catching.

When washing or garment washing is performed, the sliders or teeth may contact other garments. Before use, confirm in advance the closed position during washing, protection of the pulls, and discoloration or coating wear on metal parts, including the fabric and finishing process used.

In prototypes, check opening and closing to both ends, the movement when the two sliders come close together, and waviness after sewing. In particular, for a two way separator specification, verify insertion into the opening device and the operability of the lower slider in a condition close to actual use.

Frequently Asked Questions

Are a double slider and a two way separator zipper the same?

No, they do not mean the same thing. A double slider refers to a structure with two sliders, while a two way separator zipper refers mainly to an open-end specification that can be opened and closed from the top and bottom. Two sliders are usually used in two way separator products, but not all double sliders are two way separators.

Where do you measure the length of a double slider?

Generally, the effective length from the top stop to the bottom stop is checked with the zipper closed. However, the standard may differ for types with an opening device, continuous chain, or special stop specifications. When ordering, confirm not only the required length but also the measurement standard and the excess at the tape ends in the specification sheet.

Can a double slider be added later?

Usually, it is not easy to add only the sliders later to a finished closed zipper. The end stops or opening device must be removed, and the teeth or coil may be damaged. Decide the required opening method at the planning stage and select a finished product with two sliders or a compatible chain.