The clean, simplified sill was initially introduced as part of the Altherm, First and Vantage residential ranges of sliding doors but has now been rolled out to include the APL Architectural Series. 

Another key feature of the system – the use of easy-glide rollers for effortless opening and closing – is particularly appropriate for the Architectural Series where sliding panels are often specified in large sizes with heavier weights.

As shown in the accompanying graphic, the raised track sits nearly flush with the internal frame and outside threshold. In the installation shown, the sill frame has been rebated into the floor pad and a flush drainage grate is shown on the outside.  The elevated roller track also conceals the drainage system for a tidier appearance.

Note that all APL sliders and bi-folding systems are bottom rolling rather than top hung.  This is to ensure that in all cases the weight is carried where it is best supported — on the sill rather than from the lintel. The possibility of lintel sag and binding doors is minimised.