Stick the first row of seagull deterrent seagull spikes towards the front of the ledge, so that the spikes fully protect the leading edge. Press down firmly so the glue oozes out through the little holes. If the gap behind the pins is greater than 4 inches (10cm) seagulls may get in behind. It is therefore necessary to install another row of spikes into this space to block it. For very wide ledges 3 or more rows of spikes may be required remembering to leave as small a gap as possible between the tops of the pins of adjacent rows.