To put one‘s foot on the side of the animal at the time of slaughtering

Narrated Anas:

The Prophet used to offer as sacrifices, two horned rams, black and white in color, and used to put his foot on their sides and slaughter them with his own hands.

حَدَّثَنَا حَجَّاجُ بْنُ مِنْهَالٍ، حَدَّثَنَا هَمَّامٌ، عَنْ قَتَادَةَ، حَدَّثَنَا أَنَسٌ ـ رضى الله عنه ـ أَنَّ النَّبِيَّ ﷺ كَانَ يُضَحِّي بِكَبْشَيْنِ أَمْلَحَيْنِ أَقْرَنَيْنِ، وَوَضَعَ رِجْلَهُ عَلَى صَفْحَتِهِمَا، وَيَذْبَحُهُمَا بِيَدِهِ.