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Door-to-door is a canvassing technique that is generally used for sales, marketing, advertising, or campaigning, in which the person or persons walk from the door of one house to the door of another, trying to sell or advertise a product or service to the general public or gather information. People who use this sales approach are often called traveling salesmen, or the archaic name drummer, to "drum up" business. A variant of this involves cold calling first, when another sales representative attempts to gain agreement that a salesperson should visit.
Historically, products sold door-to-door will be of the same variety that can be purchased at large discount stores. The products accounting for the largest share of direct-sales revenue include cleaning supplies, cleaning equipment, appliances, magazine subscriptions, and home improvement products. The largest subset of these would be the home improvement products/services where items sold could be new or repaired roofs, siding, new replacement windows, and decorative stone. As of 2008[update] the business model of many companies that participate in this type of direct marketing has changed with the growth of the Information Age. Products sold door-to-door are now more likely to be more subtle in nature: such as sheets of coupons to events or local businesses, season tickets to local professional sports teams (both of these are known in the industry as "Cert [or certificate] Sales", or subscriptions to home television services or broadband internet services. Telecommunications companies like Verizon Communications (FiOS), Comcast (Cable television and internet) and AT&T (U-verse) all contract with various marketing companies for nationwide sales fulfillment at the residential level. While the practice of the salesman carrying a bag of goods on his shoulder to sell to the public declined with advances made in technology and internet selling, there has been a resurgence of door-to-door selling in recent years, especially in the energy and solar industries (Solar City) (Vivint Solar Inc.). 
Banning and Regulation
In the United States, some communities attempted to criminalize this form of selling by passing what is known as a Green River Ordinance which bans all door-to-door sales. In 1933, the United States Court of Appeals for the 10th Circuit upheld such a law valid  but in 1976 the Supreme Court extended the First Amendment to commercial speech and in 1980 set forth a four-pronged test regarding the regulation of door-to-door selling:
- The pitch itself must not regard things that are in themselves illegal and must be truthful to be protected by the First Amendment.
- Assertive governmental interest is substantial.
- The regulation directly advances point 2.
- If the regulation is necessary to serve that interest (i.e. demonstrating “no solicitation” signs and already existing trespass laws are not sufficient).
If a regulation meets these criteria, it is most likely legal.
A similar, but unrelated term is door-to-door shipping,[clarification needed] which is a service provided by many international shipping companies. The quoted price of this service includes all shipping, handling, import and customs duties, making it a hassle-free option for customers to import goods from one jurisdiction to another. This is compared to standard shipping, the price of which typically includes only the expenses incurred by the shipping company in transferring the object from one place to another. Customs fees, import taxes and other tariffs may contribute substantially to this base price before the item ever arrives.
Door to doorers
In Ireland the distribution of bags and tags by charities collecting clothes and other items has become widespread. The people that distribute these items have become known as the door to doorers.
Law enforcement and detective work
Police detectives many times will go door-to-door at residences that exist nearby a crime scene, to see if the victim or perp may have known (or may have been known by) any of the residents in the general vicinity, or to gather information from potential witnesses.
- Sweet, Cassandra. "Solar City Aims to Cut Marketing Costs as Competition Heats Up". The Wall Street Journal (wsj.com). Wall Street Journal. Retrieved 1/17/2017. Check date values in:
- "Door-todoor Sales: The Forgotten Channel". Boston Consulting Group.
- Town of Green River v. Fuller Brush Co. (1933) 65 F.2d 112
- Virginia State Board of Pharmacy v. Virginia Citizens Consumer Council, Inc. (1976) 425 U.S. 748 (96 S.Ct. 1817)
- Central Hudson Gas & Electric Corp v. Public Service Comm. (1980) 447 U.S. 557, (100 S.Ct. 2343)
- Edenfield v. Fane: Project 80’s Inc. v. Cit of Pocatello (1988) 876 F.2d 711.
- Nyberg, Ramesh - Cover Story - Going Door to Door - Police Patrol - The Law Enforcement Magazine. policemag.com. July 1, 2006. Retrieved September 19, 2016.