The office of mantling being a purely decorative one suggests that its treatment, as form, should be such as to support and supplement the lines of the shield and its contents, and to assist in linking together the whole composition. It will therefore avail itself of the well-known power of curves to emphasize what they enclose and will find endless variety of design in the way its lines may be made to help each other in direction and force. [Illustration: Bookplate of John Stabius, Professor of Mathematics. Dürer.] [Illustration: Arms of Kress of Kressenstein. School of Dürer.] [Illustration: Arms of Don Pero Lasso di Castilla. German, 16th Century.] [Illustration: Armorials by Dürer.] The facility of folding over the edges will be found extremely useful in correcting balance as well in form as in tone and colour, and its use in this way is practically without limit. Such foldings should of course be designed in due relation to the general direction of the mantling, so as to assist its swing and flow, or else be obviously and intentionally opposed to it. In other words, there should be intention in every detail. It will also be noticed how valuable are straight lines, either in the Arms or as the top of the shield, to play against the curves. It has been indicated that the treatment as regards form is practically untrammelled, but as to colour there are certain rules that must be observed. In the Middle Ages there were no rules other than sumptuary laws, to which it is probably due that ermine came to be painted on mantlings and caps of maintenance in the same conventional way that it appeared on the shield. Otherwise, mantlings were merely governed by fancy until late in the sixteenth century, except that in the latter part of that period it had become customary for those of Peers to be doubled, i.e. lined, with Ermine. With the seventeenth century began a uniform mantling of Gules; doubled with Ermine for Peers and with Argent for those below that rank. Perhaps the colours were considered national as being taken from St. George’s cross on its argent field. The present rule is for the mantling to be of the colour and metal first mentioned in the blazon of the arms, as the torse does, and it dates from the end of the eighteenth century. The exceptions to this general rule are as follows:--The Sovereign’s and the Heir Apparent’s arms are mantled Or, and doubled ermine, as also are those of the other Princes of the Blood Royal. Peers formerly used the first colours of their blazon also doubled with ermine, as they still do in Scotland, but otherwise they now follow the general rule. However one may regret the older custom which produced variety of colour in the surroundings of the arms themselves and so gave scope for much beautiful arrangement, the established custom should certainly be observed, however reluctantly, and colour relief be obtained in other ways; such as by treatment of the background where such is practicable. Of course