In liquid crystal dot-matrix displays light may leak through the display area between the pixels. To obtain sufficient contrast this non-pixel area has to be made non-transmissive. For ferroelectric liquid crystal (FLC) displays this may be done by switching the material in the gaps between the picture elements to a non-transmissive state by the stray electric fields that occur during application of voltages to the pixel electrodes. This is experimentally studied for test cells with an electrically modified smectic layer structure. The gap region considered is an asymmetric environment of the FLC material, as the transparent conductive coating has been removed on one substrate, whereas on the other substrate a conductor covers the glass. The FLC molecules in the non-pixel area prefer to direct their dipoles towards the covered substrate. To switch the FLC material with the stray electric fields, it is a prerequisite to outweigh this preference. We made spatially resolved observations for various gap widths and various applied voltages on 2 μm thick FLC layers. With bipolar voltage pulses of 64 μs width each, amplitudes of about 25 V are needed to switch the FLC in 3·2 or 4·0 μm wide gaps. It was found to be more difficult to switch gaps that, are 7 μm wide than was anticipated on the basis of the results for 4 μm gaps. This is attributed to the surface polarization charge due to the FLC permanent dipoles built up at the FLC-glass interface. Experimental results supporting this explanation are presented.