Reconstruction of the sheets by using minimal differences in the stamps to determine the position of every stamp in the sheet.
Way of working:
  1)Search the slight defects on the stamp.
2) Is this a constant defect? This means: are the defects accidental or do they repeat themselves on each stamp on the same place.
3)Determination of the position of the stamp by using paires,strips,corner stamps.
On the de Merode set, the 5 c and the 20 c where printed in two different editions. In each of the colours one can find constant defects. The red crosses of the 5 c and 20 c are printed with the same lithografic stone,so when we find a red-coloured constant defect on the 5 c,this also must be found on the 20 c in the same place.
Using this method we can determine the position of the stamps of the 20 c, starting from a known defect of the 5 c.
But several defects came into being during the printing, and are therefore not found on both values.
For example the variety "red rectangle" is only found on the 5 c, so the 20 c was printed first, and later a ' scratch ' was made by manipulating the stone with the red crosses.