biassed towards the edge 13c and the edge 10a which are both fixed against lateral movement so that the seam is here pressed open this resilient biassing of the tongue 14 enables occasional bulges and thickenings of the fabrics to be accommodated as for example when belts or loops are to be incorporated into the seam at this point or somewhere between this point and the position shown in fig1 a steam is injected into the seam see fig2 and 3 immediately after leaving the edges 13c and 10a the seam allowances are folded further back by the tongue 14 which now has a channel 14b defined between a base 14d and a resiliently mounted upper iorn 16 into which the blade 15 holds the seam the blade 15 is like the edges 13c and 10a fixed against lateral displacement and the resilient bias on the tongue 14 urges the seam on to the blade 15 directly after this the channel 14b widens into a slot between the base 14d and the upper iron 16 which is mounted on the tongue 14 and biassed down towards the base 14d but with an adjustable minimum spacing fixed by a stop 17 the blade 15 still holds the seam between base 14d and upper iron 16 which presses the seam on to the blade 15 while allowing.