All horizontal sliding panels should be removed whilst preparing and drilling the outerframe. Once packed and aligned, two or three screws down each side (excluding the bottom track) should be used to secure. Be aware that in the case of horizontal sliders the track must be flat and level, if it is tipped even slightly the Fitch catches may not align correctly.
The sliding panels can be lifted into place by dropping the wheels into the track first and ensuring the panel is the correct way up with the nylon wheel blocks at the bottom. It is important to make sure the panel is securely pressed down onto the wheel carriers and can slide freely to ensure the outer frame is fitted plumb and square.