(a) Nafi' narrates from Sayyiduna Ibn Umar (may Allah be pleased with them both) that when the Prophet (peace and blessings be upon him) went out for Eid, he would order a spear. It would be brought in front of him (peace and blessings be upon him), and he (peace and blessings be upon him) would take it as a sutrah (screen), and the people would be with him (peace and blessings be upon him). He (peace and blessings be upon him) did the same while travelling. Then the rulers adopted this practice.
(b) Makhul (may Allah have mercy on him) said: A spear or the like used to be carried with him (peace and blessings be upon him) so that he (peace and blessings be upon him) could take it as a sutrah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة العيدين / 6170