In cities, it may indicate a drug dealer, whether it be in front of a house or on a street corner. Many times, it is teenagers “marking their territory”.
They may be gang signs indicating certain illegal actions may be performed here, illegal substances bought here, or high ranking gang members live here. Perhaps it is best to leave the area quickly.
An old urban legend is that where there are gym shoes thrown over electrical and phone wires means there are drug dealers living near by.
Because tennis shoes have laces on them. People think it is funny to tie the laces of the shoes together in a knot and throw them up and try to get them to land on the telephone wire and stay there stuck. It is just a weird thing people do.
When we were younger we used to throw gym shoes on telephone poles. We’d use gym shoes because they can be easily tied together.