Nafi' narrates from Sayyiduna Ibn Umar (may Allah be pleased with them both) that whenever the Prophet (peace and blessings be upon him) went out to the Eid prayer ground on the day of Eid al-Fitr or Eid al-Adha, a spear would be brought in front of him (peace and blessings be upon him); it would be planted in the Eid prayer ground and he (peace and blessings be upon him) would take it as a sutrah (screen). That was an open space; there was no building there by which a sutrah could be made. So the Prophet (peace and blessings be upon him) would order the spear to be brought, and it would be planted in front of him (peace and blessings be upon him), and he (peace and blessings be upon him) would pray facing it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة العيدين / 6169