When you place in front of you something such as the back of a saddle, then there is no harm if someone passes in front of you (i.e. the other side of it).  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا جَعَلْتَ بَيْنَ يَدَيْكَ مِثْلَ مُؤَخَّرَةِ الرَّحْلِ فَلاَ يَضُرُّكَ مَنْ مَرَّ بَيْنَ يَدَيْكَ  

The back of the saddle is (about) one cubit (in height) or more than that.  

آخِرَةُ الرَّحْلِ ذِرَاعٌ فَمَا فَوْقَهُ  

When the Messenger of Allah ﷺ would go out (for prayer) on the day of 'Id, he ordered to bring a lance, it was then setup in front of him and he would pray in its direction, and the people (stood) behind him. He used to do so during journey ; hence the rulers would take it (lance with them).  

أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ إِذَا خَرَجَ يَوْمَ الْعِيدِ أَمَرَ بِالْحَرْبَةِ فَتُوضَعَ بَيْنَ يَدَيْهِ فَيُصَلِّي إِلَيْهَا وَالنَّاسُ وَرَاءَهُ وَكَانَ يَفْعَلُ ذَلِكَ فِي السَّفَرِ فَمِنْ ثَمَّ اتَّخَذَهَا الأُمَرَاءُ  

The Prophet ﷺ led them in prayer at al-Batha', with a staff set up in front of him. (He prayed) two rak'ahs of the Zuhr prayer and two rak'ahs of the 'Asr prayer. The women and the donkeys would pass in front of the staff.  

أَنَّ النَّبِيَّ ﷺ صَلَّى بِهِمْ بِالْبَطْحَاءِ وَبَيْنَ يَدَيْهِ عَنَزَةٌ الظُّهْرَ رَكْعَتَيْنِ وَالْعَصْرَ رَكْعَتَيْنِ يَمُرُّ خَلْفَ الْعَنَزَةِ الْمَرْأَةُ وَالْحِمَارُ