Al Thibault sent this tip about the INSUNITS variable and why you need to know how it works.

"Have you ever inserted a block or an entire drawing into your current drawing and noticed that it 'magically' scaled upon insertion? It either came in way too small or too big and it's driving you crazy.

"There are several different combinations of insertion unit variables that you need to be aware of in both the source (block) drawing and the target (current) drawing.

"First, in both the source (block) and target (current) drawings you'll need to look at the INSUNITS variable. This variable is stored in the drawing so it could change from drawing to drawing.

"This is the value shown below that you can access from the Format pulldown - Units.

"For example, in the source (block) drawing, if this is set at inches and that file is inserted into the target (current) drawing where it is set at feet, it will be scaled by the ratio of the two units. In this case, 1 foot/12 inches so the block is scaled at 1/12th the size when inserted.

"Likewise, if the source (block) drawing INSUNITS is set to feet and is inserted into the target (current) drawing set to inches, it will be scaled x 12 when inserted. (12 inches/foot). "Second, another option for INSUNITS is Unitless. This setting can cause headaches if you don't understand how AutoCAD treats a file with this setting.

"If either the source or target INSUNITS variable is set to Unitless, AutoCAD will look to the settings below to scale, or not scale, the drawing. (Tools -Options - User Preferences).

"The two system variables that AutoCAD will look to when handling scaling with Unitless settings, and stored in the computer registry, are INUNITSDEFSOURCE and INSUNITSDEFTARGET.

"Example: If the source (block) drawing's INSUNITS is set to Unitless and is inserted into a drawing whose INUNITSDEFSOURCE is set to feet, AutoCAD will treat it as feet and insert it based on that unit.

"Let's say the target (current) drawing's INSUNITS is set to feet. The source (block) is now treated as feet because INUNITSDEFSOURCE is set to feet in the target. Feet inserted into the target file feet, so there will be no scaling."

Notes from Cadalyst Tip Patrol: This is a great tip and is very important to understand. The INSUNITS setting is often change in the dialog box that opens when you type UNITS on the command line. Sometimes users mistakenly think this sets the type of units for the drawing but it doesn’t, not really. It tells AutoCAD that you want your units to be in feet, meters, etc. (or even light years!). That way, when you insert a block or other file AutoCAD will know how to interpret the inserted blocks units. It can be very helpful when you get drawings from outside sources that may be using different units than you. I suggest you set it up accordingly in your template files.