Establishing the Sutrah
Just before Prayer a person must establish a Sutrah/This is a Tall Object About The Height Of A Saddle, Just Beyond the Place of Prostration, Within Which Nothing Should Pass)
Place anything (about the height
of a saddle) just beyond the place of prostration.
Things that can be used are: a wall,
bed, tall pillow, tall purse, tall stick, tree, etc. Anything that breaks the
path between the person praying and someone who "may" need to pass in front.
It's best to pray facing a wall, bed, or
any other type of tall object, so that there will be no need for someone to pass
directly in front. Do not mind anyone
who passes beyond the sutrah.
The Prophet (SAW) said, "Do not pray except towards a sutrah, and do not let anyone pass in front of you, but if someone continues (to try to pass) then fight him, for he has a companion (i.e. a Shaitan) with him." (Sahih - Al-Bukhari and Ahmad)
"When he (SAW) prayed (in an open space where there was nothing to use as a sutrah) he would plant a spear in the ground in front of him and pray towards it with the people behind him." (Sahih - Al-Bukhari and Muslim)The Prophet (SAW) said, "When one of you places in front of him something such as the stick on the end of a saddle, he should pray and not mind anyone who passes beyond it." (Sahih - Muslim and Abu Dawood)