| Using constraints to manipulate objects or find points is not new. They have
been used since the early releases of AutoCAD. However a surprising number of
people either don't know they exist or have never used them thinking that they
were too complicated. By adding a toolbar
button with an arrow to help quickly reference what they do we help in allowing them to be
used by more people. When locating a point it is often not possible to find the point needed by
simply using an object snap. Either the geometry is too complex or the point is
not able to be found using snaps on the objects available. Two ways to help in
this endeavor is the use of the Hold-X and Hold-Y commands.
These commands are found in the
APS-2008 object snap toolbar. Typically the
MID2PT command's button (
)will show at the top until replaced.
Both of these buttons will work anytime a point is needed in a command.
The Hold-X command allows you to fix the X value of the point to be selected.
When selecting a placement point it is like the object is in a groove and while
"rubber-banding" will slide vertically up and down the screen as you move your
cursor. For an example we are moving a rectangle directly up until it's top
aligns with the midpoint of an arc.
![]()
In the video above, the top right corner is the base point of the rectangle
to be moved. When the Hold-X (
 ) toolbar button is
pressed the X value from the base point is locked in and any subsequent point
will only supply the Y and Z values for the second point. This has the effect of
making the rectangle slide up and down as shown above.
Since in our example we wanted to align the top of the rectangle with the
midpoint of the arc, we would use the midpoint object snap and select the
midpoint of the arc.
The rectangle will move directly up so that the top is even with the midpoint
of the arc. The Hold-X command can be combined with object snaps and other
commands like MID2PT to help you locate
points without having to draw "construction lines" to snap to.
The Hold-Y command is similar to the Hold-X command described above but
instead of fixing the X value it fixes the Y value. This has the effect of
making the object slide left and right on the screen as you move your cursor.
For an example we are moving a rectangle directly to the right until it's left
side aligns with the leftmost (quadrant) point of a circle.
![]()
In the video above, the top right corner is the base point of the rectangle
to be moved. When the Hold-X (
 ) toolbar button is
pressed the X value from the base point is locked in and any subsequent point
will only supply the Y and Z values for the second point. This has the effect of
making the rectangle slide up and down as shown in the above video.
Since in our example we wanted to align the left side of the rectangle with
the leftmost point of the circle, we would use the quadrant object snap and
select the left side of the circle.
The rectangle will move directly to the right so that the left side is even
with the leftmost (quadrant) point of the arc. The Hold-Y command can be
combined with object snaps and other commands like
MID2PT to help you locate points without
having to draw "construction lines" to snap to.
Using combinations of constraint commands can locate points based on a vast
array of geometric situations. We will show you one such example below. The
possible combinations of various constraints is only limited by your
imagination.
For this example we would like to move the rectangle shown straight up so
that it's midpoint is exactly half way between the two circles
Select the MOVE command and select the midpoint of the rectangle as the base
point.
Press the Hold-X (
) toolbar button
Select the Mid2Pt (
) toolbar button
and then select the center point of the first circle
Select the center point of the second circle
The rectangle has been moved straight up and is now exactly half way between
the circles. |
