I'd like to use the following model and modify it (a caster with brake and base for fixing to a table):
http://sketchup.google.com/3dwarehouse/details?mid=689d960f13da57a6d3dad974dc098fa1&prevstart=24

I import the model but am not sure how to do the following - would appreciate a pointer:

(a)How does one measure and scale the circumference of the wheel eg the red and or black parts ?
(b)If you look at the caster on the side opposite to the breaking mechanism, the base for mounting
to the table is extending a distance further out than the circumference of the wheel - how
do I measure that distance in case I want to move the base ?
(c)If I need to delete the base and the short cylinder on which it rests, how would I add another
cylinder and different base so that they are properly centered or off-center as needed
(having trouble with alignment and moving eg a square base to center it on a cylinder)

I'm a beginner but I'll allow myself to be a bit philosophical
as I've come to a conclusion which may or may not mean anything
to you - besides going through all the sketchup videos and duplicating
the steps in the videos and understanding the basics of the tools, my tip
is that you have to stop thinking about drawing (lines, shapes etc.) and
start thinking creatively about geometry, components, groups
and how the tools can be combined in magical ways to draw what you need.
When you have some spare time, pick some questions on the forum on how
something was done and you'll further speed up filling your bag of tricks.

Jean Lemire - thank you very much ! - I've got it now.
It seems to me that it takes a while to go from
making a rather mechanical usage of the tool to
creatively thinking how to do certain things - I'm not
by any means there, but I feel I've got a sense for
what is needed to be creative and efficient with the
tool - now back to practicing and asking more questions .

Thanks for the replies / your trouble - very much appreciated !
Here's a few more questions if you don't mind :

Gaieus - must have been very tired that day - forgot it was a "gmail"
email address and not "google"- looks like it was accepted anyway

Jean Lemire - Aquarium frame scenes:
Scene 7 - (excuse a little diversion )
I believe I understand the difference between entity (point, line etc.), group (grouping of entities), object (I believe it is just some group of entities eg a chair, cube, car etc, and component - something which can be instantiated (special form of grouping).
My problem comes with intersections. I think I understand
-intersect with model (intersection of everything)
-intersect with selected (means of intersecting between only what is selected

• but I don't understand when intersect with context is used and whether the three different types of interesects work for different combinations of component, group and set of entities - or is there something simple which I haven't absorbed which tells you when intersect with context is not applicable.

Scene 10
To join the two pieces I guess you select one component and move it by anchoring to a corner and moving it to its mating corner on the other piece , then exploded both components and erased the junction lines- correct ?

Scene 17
Could you please explain how you did this? (I made one piece a component, used guide lines to get the center, rotated the component by 90 and entered 3x to get the 4 pieces)

When you did the second method of creating the aquarium, I remembered the old days when the maths teacher used to mention what was the most elegant solution – thanks – that was very interesting

mac1 – will check the tool you mention, but could you explain a bit more what you meant – I'm afraid I'm too much of a newbie to have followed it.

I'm relatively new to sketchup & the smart/efficient
ways to model, so would appreciate some pointers. I have dug
through the video tutorials,found the engineering toolbox plugin
and have started working. As a simple example, I would
like to model a fish tank made of steel angle/L profile where
the ends of each piece of steel angle are mitered at 45 degrees
both towards the other pieces in the same plane (eg the
base and top sections)as well as to the vertical sections
(just to make it hard enough to learn enough to move a
few steps forward ).

I would like to do all this in such a way that I can scale
the fish tank without changing the size of profile of the
steel angle to see the proportions before
finalizing the model.

Engineering toolbox generates a desired length of steel
angle. The next step I took was to use a square shape
angled via the rotate tool and intersecting the angle
to get the 45 degree miter / that's as far as I got

• could someone briefly describe
  the steps (and maybe thinking behind them) to model
  the fish tank ?