The invention is based on the realization that feedback control for the vertical drive of a pin head becomes unnecessary if one instead prealigns the relative heights of the spotting surface and the well plates such that the pins in the pin head are lowered to the same absolute height both for picking up liquid from the well plates and depositing it onto the spotting surface. By aligning the heights of the well plates and spotting surfaces, the vertical drive of the pin head needs only to be able to reproducibly and accurately arrive at a single lowered position. A pin head can provide this functionality by having a mechanically defined bottom point, obviating the need for a complex and costly feedback control system for height determination of the pins. A simple, low-cost micro-arrayer can thus be provided.