When is a silverfish not a silverfish?
When I tried hands-on at editing landuse plans, I realized upon zooming in, the existence of 'silverfishs' here and there. This was probably because these digital plans had their roots in CAD drawings and I assume that their occurrence would not been had they been created by GIS software instead. Anyway, I did not have any problem deleting them until I came across some which I simply could not. I was baffled. No matter how much I zoomed in, I just could not delete the stubborn silverfish not until I accidentally clicked and moved a node away from the centre of the line exposing it to be a polygon hiding behind the skirt of a line. I then selected that polygon and successfully deleted it. Sometimes, the third node overlaps seamlessly behind a vertex node giving the impression it is a simple line and until you move it, you won't hear it say "Trick you!" Conclusion: What you see on a GIS layout not necessarily is what it is.