The square acaemic cap, sometimes called colloquially a mortarboard (because of its similarity in appearance to the hawk used by bricklayers to hold mortar) or Oxford cap, is an item of academic headdress consisting of a horizontal square board fixed upon a skull-cap, with a tassel, or liripipe, attached to the center. In the UK and the U.S., it is commonly referred to informally in conjunction with an academic gown worn as a cap and gown. It is also often termed a square, trencher, or corner-cap in the UK and Australia. In the U.S., it is usually referred to more generically as a mortarboard, or simply cap.