This function is very versatile. Not only is it used to create blotch layers, also known as choke layers because they sit perfectly around other layers, but also platform layers, named so because they sit under other, often tonal layers, to give them a boost in colour and tone.

Pad layers are often used to coat the substrate prior to printing the design. Because they are always the first layer to the printed (in conventional printing) they are always in position 1 in the Layers Palette. They are usually the same colour in all colourways (but not always!)

Adding blotch/choke layers

This is a 1 bit layer that fits around other layers in your design. It works by filling any areas of your design which do not have visible pixels with colour, so it is important to consider which layers should and should not be visible at the time of creating a blotch layer. If a layer is visible, this area will not be affected by the newly created blotch layer.

1. If you have an image in your file, make this invisible, along with any other layers you want to blotch to sit under. In the example below, the blotch layer is going to sit around all layer, except layer number 4, because this has been made invisible. Therefore, the blotch layer will fill its space.
2. Select Make Blotch from the Separate Menu. A layer is added to the bottom of the layer list, which fills all areas of the design that were invisible.
3. Reposition and recolour the new blotch layer accordingly.

Adding platform layers

This is a 1 bit layer that fills exactly the same area as another layer, which is often tonal.  The two layers print in the same position but the platform layer is printed first and boosts the tonal layer.

1. If you have an image in the file, make this, and the layer you are creating a platform for invisible.
2. Select Make Blotch from the Separate Menu.  The only area to be filled with colour will be the area usually occupied by the tonal layer.
3. Reposition this new layer to sit above the tonal layer in your Layers Palette, and recolour accordingly. This layer will now act as a platform for the tonal layer.

Adding a pad layer

Make Pad is a very useful function that can be used to create a solid layer which fills the whole design.  The software ignores which layers are visible and invisible and always creates a complete pad layer when you select this function. Ensure there are no selections in the file when you select Make Pad from the Separate Menu, otherwise only the selected area will be filled on the new layer.

1. Make sure there are no selections in the file (use the keyboard shortcut ⌘D if you are not sure), and then select Make Pad from the Separate Menu. This adds a 1 bit layer at the top of the list in the Layers Palette.
   
   

2. Recolour the pad layer accordingly. In the snapshot below, the original separation is shown on the left, while the separation with the pad applied is shown on the right.