"Laid paper was handmade in wooden moulds that had many wires stretched
across its frame. This would hold paper pulp that had previously been prepared in a large vat. Also stretched across the mould at right angles to the multitudes of wires, were heavier wires placed at regular intervals to support to smaller wires. The result was that these wires left a very recognizable pattern on each sheet of paper produced. The impressions left by the numerous cross wires were called "laid" lines. This, also, authenticates the age of the paper. It is generally agreed that laid paper was made up until about c1800, when high quality wove paper began being made in quantity. About half of all laid paper had a watermark consisting of a design or initials"1.
1.Ron Flynn (www.ronflynn.com)