4. =Soundness of constructional methods.=--This rule is really contained in those that have preceded it, but some notice should be paid to the various methods of fastening different plates and portions of the suit together. There are many ingenious forms of turning hook and pin by which these plates can be joined or taken apart at will (page 55). The sliding rivet is one of the most important of these constructional details. The lower end of the rivet is burred over the back of the lower plate, and the upper plate has a slot cut of less width than the rivet-head, but sufficiently long to allow the plate to move backwards and forwards, generally from three-quarters to one inch (page 52). 5. =Subservience of decoration to the preceding rules.=--The best suits are practically undecorated, but at the same time there are many which are ornamented with incised or engraved lines and gilding which do not detract from the utility of the armour. This last rule is best understood by examples of the breach rather than the observance; so we may take the rules in order and see how each was broken during that period known as the Renaissance. (1) The “glancing surface” was destroyed by elaborate embossing, generally of meaningless designs, in which the point or edge of a weapon would catch. (2) The convenience was also impaired by the same methods, for the lames and different portions of the suit could not play easily one over the other if each had designs in high relief. Plates were set at unpractical angles, sometimes overlapping upwards, in which the weapon would catch and would not glance off. We find that foot-armour was made in the sixteenth and seventeenth centuries with the lames all overlapping upwards or downwards, and with no centre-plate for the tread. In the suit given to Henry, Prince of Wales, by the Prince de Joinville in 1608 (Tower, II, 17) the lames of the solleret all overlap downwards (see also Fig. 4). It will be obvious that with such a foot-covering it would be impossible to walk with ease. (3) The observance of this rule may be taken as a matter of course and its neglect has been noticed above. (4) The careless arrangement of the foot-armour, as mentioned in No. 2, is an example of the disregard of this rule. Another instance is the embossing the metal of various parts of the suit so as to simulate lames or separate plates. They do not ornament the suit and of course do not add to its convenience; they merely create a false impression and save the craftsman some labour. The same may be said of the “clous perdus” or false rivets, which are found in late suits, doing no work in the construction of the suit, but giving an appearance of constructional work which is lacking.