It is Sunnah to take a Sutrah (screen) for the Imām (leader) in congregation, and also for one who is praying alone. However, those lead in prayer by the Imām do not need Sutrah, as the Sutrah of the Imām is sufficient for them.
Abu Sa‘eed Il-Khudriy (ABPWH) narrated that the Prophet (PBUH) said in a Hadeeth, “If one of you offers prayer behind something taken as a Sutrah …” (Al-Bukhāriy no. 509, Muslim no. 505)
There are many Ahādeeth that talk about Sutrah being Sunnah. The Prophet (PBUH) used different forms of Sutrah such as a bed, wall, trunk of a tree, piece of wood, spear, goat, travel mount (camel), and so on.
Sutrah is permitted in both urban and rural/remote areas, in both travel and residence, and whether the person fears someone might pass in front of him or not. The Ahādeeth did not differentiate between urban and rural areas, and the Prophet (PBUH) used to take a Sutrah whether in travel or residence, as was reported in the Hadeeth of Abi Juhayfa. (Al-Bukhāriy no. 501, Muslim no. 503)
The distance between one who is praying and the Sutrah is to be such that a goat could pass.
Sahl Ubn Sa‘d Is-Sa‘idiy narrated, “The distance between the place of prayer of the Prophet and the wall (i.e. Sutrah) was such that a goat could pass.” (Al-Bukhāriy no. 496, Mulsim no. 508)
Imām Ahmad and Abū Dāwood stated that the distance between the Prophet (PBUH) and the Sutrah would usually be about three cubits.
Abu Sa‘eed Il-Khudriy (ABPWH) reported that Allāh’s Messenger (PBUH) ordered that one who is praying should stop anyone from passing in front of him in order to preserve the sacredness of the place of prayer. (Muslim no. 505)
Moreover, a woman passing in front of a person who is praying should also be prevented as this would invalidate the prayer according to the Hadeeth of Muslim narrated by Abi Dtharr. The Hadeeth is reported by Imām Muslim in his Saheeh collection.
This is the third situation where the use of Siwāk is recommended.
This is proven by the following Hadeeth:
Abu Hurayrah (ABPWH) narrated that the Prophet (PBUH) said, “If it was not for the fact that I may be overburdening my nation, I would have ordered them to clean their teeth with the Siwāk before every prayer.” (Al-Bukhāriy no. 887)