Badeken

Question: What is the source for the custom of "badeken" - the hatan (groom) covers the face of the kalah (bride) with a veil, prior to the marriage ceremony?

Answer: Various reasons and sources are given for this custom. the most fundamental may be that which is indicated in Tosafot (Tractate Yoma 13b s.v. le-hada amar lah) and cited in Shulhan Arukh by ReMA (Even ha-Ezer, chpt. 55, paragraph 1). There are two stages to Jewish marriage: arusin and nisuin. Arusin is, nowadays, usually accomplished by the hatan giving the kalah a ring. There are various opinions regarding how nisuin is accomplished. The custom is therefore to do as many potential acts of nisuin as possible. According to Tosafot, the covering of the kalah with the hinuma (veil) is an act of nisuin. This may be the source for the custom of badeken. To learn more about this custom and Jewish marriage see the following:
http://www.chabad.org/library/article_cdo/aid/477333/jewish/Badeken-Veiling.htm
http://www.jewishencyclopedia.com/view.jsp?artid=995&letter=B
http://www.jewishencyclopedia.com/view.jsp?artid=215&letter=M