Reflfit and reflpol model your sample as a sequence of layers. Reflfit organizes the layers into sections T=Top, M=Middle and B=Bottom, where the middle layer can repeat. Layers are identified by section and layer number.
Insert insert a new layer Delete delete an existing layer, shifting all subsequent layers Copy duplicate a layer and insert it somewhere else Move move a layer somewhere else Overwrite like copy, but replace the destination
Repeat number of repeats for middle section (reflfit only)
Due to the way the middle layers get repeated, the NR parameter should generally be two less than the actual number of repeats. One repeat should be explicitly described at the bottom of the top layers and one repeat explicitly described at the top of the bottom layers. Minimally, the bottom most top layer should be identical to the bottom most middle layer and the top most bottom layer should be identical to the top most middle layer.
Roughness number of roughness steps for the interface
Use a small number of roughness steps for quick calculation during initial fits. Use a larger number to refine the fit.
gj2 does not support repeating layers, but it does have a command for duplicating a set of layers a number of times.