What is the ruling on drawing lines in mosques to straighten rows, especially in mosques with long rows?

There is no harm in drawing lines to straighten rows in the mosque, because it helps in straightening the rows, which is a religiously commanded matter, due to the saying of the Messenger of Allah, peace and blessings be upon him: "Straighten your rows, for straightening the rows is part of the perfection of prayer." He also forbade not straightening them, due to his saying, peace and blessings be upon him: "You must straighten your rows, or Allah will cause dissension among your faces."