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To start from anew if you have objects already, you may either do lots of undos, or delete everything you see, or you can close the current file. To do this, use the closeCurrent function found as "Close Current" under the "File" file menu, or find the file node in the database, right click on it to get the context menu and choose close. It's is called "unnamed0.mvg". When you close the last file another empty file is created for you automatically. To get the viewpoint aligned with the screen use the matchUCS function found as the "Align To Z" function under the "Viewpoint" menu. Now zoom the viewpoint out so that about 8 grid square across can be seen. And pan (translate) the viewpoint to get the origin in the bottom left. Now we have a traditional piece of graph paper.
Turn on the grid snap. For this model the grid at spacing 1x1 will represent feet.
Make the out line of the bed's footprint as shown.
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It is six feet in x, four feet in y. In this model z represents height, and our foot
print is sitting on the floor. Lets draw the mattress frame now, two feet above
the footprint. To move the drawing plane to two feet above the footprint, use
the ucsPos function 
found as "Pick Origin" under the "UCS" menu. This function has only one input field,
the location of the new
origin with respect to the current coordinate system. Enter 0,0,2 to move the
drawing plane up two feet. Rotate the viewpoint around to see that the new
drawing plane is lofted above the beds footprint. Now lets draw some new lines
in the lofted drawing plane, the same shape as before.
Since the drawing is shown with a vanishing point the foot print looks smaller than the mattress frame. Dimension lines were added to prove they are the same size.
Coordinate systems can be saved for later use. You may save the current coordinate
system by using
the ucsList function 
the "Coord System List" function. The example file has it saved as "Mattress". Doing
this will enable you to quickly come back to the coordinate system.
The foot and the head of the bed will drawn in another plane. Keep in mind
this example is super simple to put emphasis on coordinates system. The bed would
normaly be created with some solids instead of a few lines. Still, drawing lines
is a typical way to mark off the key points in a model. Anyway, assuming the
drawing plane is currently "Mattress", lets move it to be aligned with the
foot of the bed. Use
the ucsRotY function 
found as the "Rot Y" function under "Coord Systems", using a 90 degree rotation.
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Now lets move the drawing
plane to the head of the bed, by using the "Origin" function under "Coord Systems",
entering 0,0,6. And draw two lines to represent the posts at the head. Deleting
the lines of the foot print gives the completed bed sketch.
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