1. Slide your try square up and down the workpiece as shown to find out which two sides form the most perfect right angles.

2. Having decided this, mark the two sides as ' face edge', with a vee mark and ' face side', with a F. Always work from these marks.

3. To scribe a cutting line, hold the try square as shown. If you are working to pencil marks, ensure that you line up the square properly.

Any slight errors made in measuring and marking will multiply when you come to start sawing and may ruin your project. The best way to avoid a mistake is to check every measure­ment twice.

Having selected the piece of timber to be worked on the work piece, inspect it carefully. With a try square, determine which are the straightest adjacent side and edge and mark them in pencil (figs. 1 and 2). Always work from these when using any measuring or marking tool this will ensure that the marks are consistent. A try square is an essential marking tool and costs very little.

For measuring, use a steel rule or boxwood rule where possible: you may need a steel tape on longer pieces of timber or boards, but this is not so accurate.

Mark out distances in pencil, using a 'vee' mark as shown in fig. 2 this tells you exactly where you have measured to and is another tip for avoiding errors. Where possible, cut out marks altogether by using the try square and rule as shown in fig. A.

Where accuracy is essential, mark cutting lines with a sharp knife preferably a marking knife not with a pencil. The scored line made by a knife is thinner, and therefore more accurate, than a pencil line. Also, it serves to break the outer fibres of the timber, thereby stopping the saw cut from fraying.

As you scribe a cutting line, use the try square to guide you (fig. 3). Your free hand should control the try square without obstructing the marking knife. Keep the stock of the try square flush against the face or edge of the work piece, with the blade flat on the surface you are marking. The edge of the blade should line up exactly with the points of the vee pencil marks.

A- Where possible, measure your timber with just a ruler and try square. This saves time and is more accurate than lining up the square with pencil marks.

B- Marking timber the wrong way. If you mark continuously right round the work peice, your lines may not meet when you get back to the starting point. With thick or rough timber, this leads to crooked cuts.

C- Marking timber the right way. Mark the face first, then the two edges, then the back. Note that both sets of parallel marks are made in the same direction, not in opposite directions.