There are many different types of moulding to suit various jobs and decorative requirements.  Whilst some moulds are used to catch and play with light and shadow, thus adding depth to the room that they are used in, others are in place purely to disguise unkempt construction remnants.

Perhaps the best known mould type is the cornice.  This is the long rectangular strip of plaster which divides either the top of the wall from the ceiling perimeter or the painted or wallpapered bottom portion of a wall from the top plastered portion.  When used as a wall divider cornices can act as picture-runners or hanging rails.  Cornices are generally made from white plaster (but can be carved from wood or moulded in plastic).  Some are quite simple, with ovolo, cyma or ogee designs determining the way the light and shade hits the cornice.  Others are incredibly intricate with detailed carvings.

Another popular type of moulding is the ceiling centre or ceiling round.  The ceiling round is almost always circular and it's design is determined by the architectural period.  This means that an Edwardian house should have Edwardian style ceiling rounds, and so forth.  Like cornices, ceiling rounds vary in design from being quite basic to incredibly intricate, with fruit, flowers and birds being popular motifs.