The Prophet Muhammed (SAW) said: “When one of you prays, pray towards a Sutrah. Stand close to it and do not let anyone pass between you and it.” – Abu Dawood

The above hadith applies to both men and women, regardless of whether the prayer is in the home or Masjid. This practice is more than a Sunnah as the use of a Sutrah is considered compulsory by majority of scholars although there are evidences that show that the Prophet (SAW) did at times pray without a Sutrah - this is allowed in the case where one does not fear that someone will walk in front of him. The Sutrah can be anything one puts in from of him when he is facing the Qiblah to screen those passing in front of him from going one side to the other. It could be a wall, a person or a piece of wood and there is no limit to its width. It should be the height of the back of a saddle (about a hand span). It is related that the Messenger of Allah (SAW) prayed towards a column in his masjid, towards a tree and even a bed upon which Aisah (RA) was laying on. There should be sufficient room for the sajdah – about three arm spans. In a congregational prayer, the imam is the sutrah of the people praying behind him; hence the reason why it is permissible to walk between the lines of the people if there is an urgent need to. 

If the person who passes in front of another person in Salah knew the magnitude of his sin, he would prefer to wait for 40 (days, months or years) rather than to pass in front of him. - Bukhari

Benefits of Using a Sutrah

• It protects the prayer from being broken as the value of a salah is reduced when one passes in front of a person praying. The salah is broken completely if a female past the age of puberty, donkey or a ‘black’ dog passes between the one praying and his sutrah.

The Prophet (SAW) said: “The prayer of a Muslim man is invalidated if he does not have in front of him something like the back of a saddle; by the passage in front of him by a woman, a donkey or a black* dog.” - Muslim (Abu Hurayrah repeats the same hadith without using the word black)

• It provides space for people to pass thus eliminating the need for them to pass directly in front of you as that is a major sin.
• It helps with concentration and improves your level of Khushoo’ as the eyes of the one praying will not wander; it would be focused on the area of before the sutrah.

Abu Sa'id said: "I heard the Prophet (SAW) say: 'If any of you prays towards a sutrah and someone tries to pass in front of you, then turn him away. If he refuses, use force for he is a devil'." - Muslim, Bukhari

And Allah (SWT)  knows best.