The forme was fixed in a cast-iron plate which was carried to and fro on a table, being received at either end by strong spiral springs.

A double machine, on the same principle,--the forme alternately passing under and giving an impression at one of two cylinders at either end of the press,--was also included in the patent of 1811.
How diligently Koenig continued to elaborate the details of his invention will be obvious from the two last patents which he took out, in 1813 and 1814.

In the first he introduced an important improvement in the inking arrangement, and a contrivance for holding and carrying on the sheet, keeping it close to the printing cylinder by means of endless tapes; while in the second, he added the following new expedients: a feeder, consisting of an endless web,--an improved arrangement of the endless tapes by inner as well as outer friskets,--an improvement of the register (that is, one page falling exactly on the back of another), by which greater accuracy of impression was also secured; and finally, an arrangement by which the sheet was thrown out of the machine, printed by the revolving cylinder on both sides.
The partners in Koenig's Patents had established a manufactory in Whitecross Street for the production of the new machines.

The workmen employed were sworn to secrecy.

They entered into an agreement by which they were liable to forfeit 100L.