I bought a pair of these off E-Bay :
They are used to align the caravan wheel ( or car if they fit ) if there is need to remove/replace the wheel.
As the Orion wheels are bolts and not studs there is nothing to hold the wheel over the bolt holes whilst you insert the bolts.
Some people use their foot to steady it but these seem a much better option in my book.
The Bailey Orion bolt size is M12 x 1.5 ( this is direct from Bailey ).
They cost round about £8 plus P&P.