Wikipedia
Linestanding or seatholding is a service provided in Washington, D.C. to lobbyists, corporate legislative offices, non-profit organizations, lawyers, and other people having an interest in matters being debated or bills being marked up by the United States House of Representatives or United States Senate. The linestanding company will send someone to Capitol Hill to stand in line well in advance of the hearing or mark-up to help the client gain entry into the hearing room with a good seat in the visitors gallery.
On October 18, 2007, freshman Senator Claire McCaskill from Missouri proposed that linestanding for registered lobbyists be made illegal. Her feeling was that lobbyists should have to stand in line with everyone else. In response to McCaskill's bill, a linestanding company wrote the following response http://www.qmsdc.com/mccaskill/ResponsetoMccaskill.pdf
In March of 2012, the Supreme Court heard an unprecedented three days of oral arguments in regards to the Affordable Care Act (President Obama's Health Care Reform Law). Linestanders stood on 1st Street NE for four days holding spaces for various State Attorneys General, industry lobbyists, healthcare professors, and other interested parties. Local media as well as national news organizations turned the outdoor proceedings into a circus. http://capitolhill.wusa9.com/news/news/100086-bizarre-business-professional-line-standing
Other examples of linestanding services include the recent service launched in Birmingham, AL as a response to the long wait times at the Jefferson County Courthouse Department of Motor Vehicles. It is geared towards individuals who have physical disabilities, the elderly, and other people who are unable to wait the average 3.5 hrs.