An obelisk is a structure for climbing plants to grow up and against, twining plants that have tendrils like one made of thin metal but you can get obelisks made of any material.
Wooden ones, wicker, metal, wire .... or a makeshift one made of bamboo canes.
Ian, i wrote a blog on one i bought !!! Think it was last year .... maybe it just feels like that though ;-)

I bought one from Aldi I have it in a pot with Morning glory (heavenly blue) growing up it. People make wigwam types out of canes for sweet pea etc; to grow up not as smart !! but you get the idea.