It is normal to remove one's shoes and set them on the rack at the vestibule while entering a mosque. This is done out of respect and to keep the inside prayer hall floor clean. (There are no seats or benches in prayer rooms, simply rows upon rows of carpets lined to face Islam's holy city of Mecca in Saudi Arabia.) Chairs are used in mosques for elders to sit with honor in front of the qibla (the direction of Kaaba) when they lead prayers. There are also chairs for children to attend mosque sessions. The use of chairs in mosques is a modern innovation that has become popular recently. In the past people sat on mats on the floor or leaned against walls for support as they prayed. Now that many more people pray together in groups, chairs provide space for everyone to have some form of support while sitting upright. An imam (a Muslim priest) leads prayers in mosques. He may be male or female. When men and women pray together, the man usually gives the sermon during weekly services called Jumu'ah. He may be accompanied by other scholars who teach during the sermon period and answer questions from the audience. Jumu'ah sermons are often long discussions about Islamic topics held in mosques all over the world every week. They can be watched online via satellite TV or streamed live via the internet. Preachers/imams can be celebrities who attract large crowds in private clubs or small towns where no other preacher is available.