Is alignment in congregational prayer rows done by the feet or by the shoulders?

Alignment in rows is done shoulder to shoulder and foot to foot. On the authority of Anas (may Allah be pleased with him), the Prophet (peace and blessings of Allah be upon him) said: "Straighten your rows, for I see you from behind my back." And one of us would stick his shoulder to his companion's shoulder and his foot to his companion's foot. And on the authority of Nu'man ibn Bashir, he said: "I saw a man among us sticking his ankle to his companion's ankle." These hadiths indicate the importance of straightening the rows, and that it is part of perfecting the prayer, and the worshipper should stick his shoulder to his companion's shoulder and his foot to his companion's foot.