but via Improbable research: Uses of Blutack for researchers.
blutak is a clay like sticky glob you can use to hang up posters.
the company's site says it has many uses.
Holds up posters, cards, children's paintings, party decorations, maps, messages, etc. Telephones and calculators to desks, ornaments to shelves, photos in albums, screws to screwdrivers, model parts during painting,etc.
Holds safety pins, keys, screws, etc. flowers and candles in place for table and flower arrangements.
Cleans fluff from fabric and dirt from typewriters, model railway tracks, etc. May be rolled and manipulated to make 3 dimensional artistic ‘models’.
For use on non porous surfaces: vinyl coated wallpapers, painted surfaces, glass, and metal.
Blutack Wikipedia page explains why it is blue:
but they note that it is non toxic if eaten, but what if you get it in your hair? Use Baby oil...
Originally Blu-Tack was white, but consumer research showed fears that children may mistake it for chewing gum, and a blue colouring was added.
and then there is claymotion films: