When guys go outsidelate at night and piss on the streets all over the place in various patterns and then in the morning go and laugh at the pattern you created.
When two girls get really wet and drag their pussies across bedsheets to see who can leave the longest pussy juice line on the sheet.
Typically both girls would be next to eachother either on their stomach or on their backs. Each girl would grind their pussy into the bedsheet while moving upwards toward the end of the bed in an attempt to leave the longest trail of pussy juice. When the juice drys it will appear shiney and slimy as if a snail had crossed the bed.
I had two girls over last night in my bed and they had a snail trailrace.