Recent photographs of Pakistan’s Special Service Group have surfaced in which members of the group are conducting mountain warfare training in the snow. Of particular interest is of the group conducting their Salat, or daily prayers. The prayers themselves aren’t so much as interesting as is what the soldiers are doing with their weapons. The M4s and in another picture, Kalashnikov patterned self-loading rifles are stuck into the snow in front of the soldiers praying, butt first.
Although not really utilized today throughout the Islamic world, the practice dates back to the early Islamic period where one would place an object in front of them so other people would know not to walk in front of them during their salat. Specifically, it is called a Sutrah, or سترة in Arabic, meaning screen, or cover. There are some Hadiths on the topic but again it isn’t in wide use today.
Wikipedia lists two Hadiths in particular–
Sahl ibn Abu Hathmah narrated: إذا صلى أحدكم إلى سترة فليدن منها لا يقطع الشيطان عليه صلاته The Prophet said: When one of you prays facing a sutrah he should keep close to it, and not let the devil interrupt his prayer.
The Messenger of Allah said: لا تصل إلا إلى سترة، ولا تدع أحداً يمر بين يديك، فإن أبى فلتقاتله؛ فإن معه القرين Pray facing a sutrah, and let no one cross in front of you while praying. If he insists, then prevent him by force because he is accompanied by shaitan.
Another resource on the topic is listed here for those fluent in Arabic.