The Handyman's Pocket Book: Pelmets and Curtain Runners.

Pelmets can be made in various materials.  Veneered plywood looks very well when arranged with contrasting veneers and finished with french polish or cellulose.  Mouldings can be applied if desired.  An alternative is to use a thin hardboard and finish with paint or cover with material.  As a rule the top is filled in entirely by the top board to which the track is screwed, though a gap can be left if it is desired to allow light to enter at the top.  Fixing is by metal angle brackets screwed beneath the top board and plugged to the wall or screwed to the window frame.  Bay windows can be arranged as in Fig. 7.  The main top boards are screwed together, and a batten fixed beneath the centre one to bring it level at the underside to enable the curtain track to be screwed up.

Large curtains to cover in french doors, etc., should overlap as in Fig. 9 as this is the only way of ensuring that they keep out drought.  The valance has a top tape which is fixed to the board with tacks or drawing pins.  The track is quite flexible so that it can be bent easily.  This makes it specially useful for bow windows as it can be taken round in a continuous length.  When no pelmet is fitted special wall brackets are used to hold the track.  These can be obtained also to hold a valance rail.