Is it permissible to mark the mosque floor to straighten the prayer rows?

There is no objection to marking the mosque floor to aid in straightening the rows, as straightening is legally required. The Prophet, peace and blessings be upon him, encouraged and desired it, and warned those who did not maintain its straightness. He, peace and blessings be upon him, said: "(Straighten your rows, for the straightening of rows is part of establishing the prayer)," and he said: "(You must straighten your rows, or Allah will cause disagreement among your faces)."