Before you can begin to mark out wood you have to have one long side flat and one edge at 90 degrees to it. This is called a face side and a face edge. Once you have achieved this you can begin to mark out using a try-square and a pencil or marking knife. These will enable you to mark your wood to thickness and width before planing or sawing. Marking to width can be done with a ruler and a marking gauge. This marks parallel lines to edges. If you want to mark out rectangular holes ready for cutting you would use a mortise gauge. Marking circles would be done with a pair of compasses.

Once you have a face edge and a face side you can accurately mark wood to length using a trysquare
and a marking knife or pencil.

Set the marking gauge to distance using a ruler. You can then place the stock of the tool against either the face side or face edge for drawing a parallel line.

A cutting gauge has a small blade and is used when marking across grain.

The mortise gauge has two spikes (or spurs) and is used for marking out rectangular holes.