In general pretty much all the wood on a given project looks the same. One key to assembling everything is being able to mark the wood quickly and easily and incontrovertibly so that if you (or anyone for that matter) picks up the piece hours, days, or months later it will be clear where it goes.
The system I use (and didn't invent - it has been around for ages) is the triangle. Here it's being used to show the sequence of glue up on a series of boards. I think the method is better than using a bunch of lines because a triangle is clearly not a stray pencil mark. Even with the pieces apart it is pretty easy to figure out where they go.
Clearly the two pieces are left and right and the top piece is clearly the top piece. If the top piece only had part of a triangle one would assume that another piece was missing on the bottom.
Front and back to a drawer - when otherwise everything matches. The notation also gives clear indication of inside and outside which is very important. And spread apart it also makes sense.
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You can put the marks on the front or the back or a project - it doesn't matter as long as you are consistent. What is important is that you are preserving the orientation of one board with respect to the next.
The last picture shows method for keeping track of your reference surfaces on a specific board is using triangles. The method that looks like an "X" is actually two "V"s put on one at a time after I first plane the face then the edge of a board.
In any case, if you find yourself getting confused if a part of a project belongs on the left or right or facing in or out, try changing your system of notation and this system of triangles might be the answer.
Note: the wood is marked in marker just to make it easy to photograph. On real projects I use pencil like everyone else.
As a beginning woodworker, tidbits like this about mark-up are nuggets of gold. It's a shame most such info seems to be presented as brief sidebars to the actual cutting, planing, etc.
02/26/2010
Mark Haas
Joel -
Suggest you use chalk instead of a pencil - it will not have to be sanded off finished surfaces.