On top of the roof of the Heichal was a fence. On top of this fence there were metal spikes, one cubit in height, known as the "Koleh Orev", literally, "the raven restrainer". * These were designed to prevent birds from landing on the roof of the Temple. Another opinion states that these spikes completely covered the roof of the Heichal. (Source: Rambam, Beit Habechira 4,3)  
Dimensions
Contents:   Part I,    Part II,    Part III,    Part IV,    Part V,    Part VI,    Part VII