Tibbs has answered your question and alluded to something else you should consider. I wrote the following for a US audience before Google SketchUp was released. Most of it still applies. Additions to this text are in green.
"Before you spend anymore time drawing in SketchUp, try doing the following. It should make some tasks, particularly drawing smaller stuff easier.
1. Go to Window>Model Info>Units. Change Architectural to Fractional. Set precision to 1/64". Uncheck Enable Length Snapping. I don't believe Fractional is an option in GSU. Choose either Archtecrtural or Decimal. Set Precision as desired--probably a couple or three places past the decimal.
2. Draw a square 36" x 36" on the ground plane. The red and green axes lay on the ground plane. Set one corner of the square at the origin (the intersection of the three axes). Use Push/Pull to pull the square up into a box 48" tall. Use the metric equivalents.
3. Click Zoom Extents. that's the magifying glass with the red arrowheads sticking out of it.
4. Set the view to Shaded. That's the tan cube next to the white cube on the tool bar.
5. Use the select tool and select the box you just drew. Delete it.
6. Save this blank drawing in the Templates folder. C:\\Program Files\@Last Software\SketchUp5\Templates. Give it some unique name. The file location may be slightly different. Maybe Google instead of @Last
7. Go to Window>Preferences>Templates and browse to find the file you just saved.
Now, when you open SketchUp all the things you set above will be done and the window will start zoomed in to allow a 36x36x48 or your metric equivalent box to fill the screen. You can change the settings if you like but these should be a pretty good starting point for drawings of woodworking projects."
