This was one of the earliest and most popular envelope systems. The plates are held in a plastic and cloth envelope, the front, covering the emulsion, is made of cloth. In use, the plate in an envelope is placed in the wooden adapter which replaces the normal dark-slide in the camera. As the draw-slide is pulled out so the cloth covering the face of the plate is rolled up and is rolled back when the draw-slide is returned. A yellow window in the back of the adapter was used to ensure that the envelope cover had rolled up correctly.

The original pattern, latter called Model A, was made in sizes from quarter-plate to whole-plate.

In 1906 a second model was brought out, called the Model B. Model B envelopes have a removable, rigid, draw-slide which is accessible from outside the adapter which does not have a draw-slide.

A model Bz was also made for cameras having a spring back where the back of the dark-slide was not accessible. In the Bz pattern the envelope pushes into the end of the adapter rather than the back.

This slide fits the Thornton-Pickard Model A Aerial Camera produced in 1915 for hand-held use from a cockpit. The slide is made of oak and is more rugged in construction than ordinary slides, there is also an interlock to prevent the door from being opened whilst the slide is withdrawn. Douglas Rendell, Thornton-Pickard Story, states that the Model A camera used the Mackenzie-Wishart slide until the summer of 1915.