# What is this mysterious thing on the vertical stabilizer of the Boeing 707?

Have you ever seen this mysterious line-shaped thing on the vertical stabilizer of a Boeing 707 or 720? What purpose does this thing do?

• Could you maybe provide a picture that is a reasonable size? May 7 '20 at 16:25

• Surely UNIVAC Coupler isn't the mainframe? May 7 '20 at 17:37