The harmonized European standard EN 14351-1 specifies uniform properties and requirements to windows and entrance doors. The visible confirmation of meeting the requirements imposed by the standard is the CE mark. Marking products with the CE symbol indicates that the products conform to European directives and guidelines and are allowed for sale and use within the entire European Union. During the transition period, from October 2006 to October 2007, the products can be marked alternatively with the CE symbol of with national codes. From October 2007 the CE symbol shall be the sole evidence that the window woodwork products are allowed to be placed on the market in the EU territory.