Blu-tack

/ (ˈbluːtæk) /

noun

trademark a type of blue, malleable, sticky material used to attach paper, card, etc to walls and other surfaces

verb

(tr) to attach (paper, card, etc) to a wall or other surface by means of this material
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012