Hello,
 
I  am having some difficulty  aligning  a soild like for example   the four legs  of a chair  to top of a circular table  to a particular point..  I have no problem  aligning  a box on top of another box.  I  tried using 3d align command ( where the first selections are made to the sources object)  and also the Align command ( where the  selections are source / destinantion  and so on). The  problem I am getting with the  chair legs  is that  I dont have a  point ( destination pt) to snap on to .So I tried the quadrants  of the table with no luck.  When I  Use the 3dAlign and do the selection on the chair legs, I find the the chair rotates through  90 degrees, for no apparent reason, before it  snaps on to the  base point quadrant of the table. Where am I going wrong. ?  The table top face is on XY Plane with legs on Z axis facing the floor  but the Chair I have it inverted ( so I can see the   the  points on the legs to snap to) . Is there a general rule   such as how UCS should be to align  objects ???

You could cheat and use some 2D geometry to get the table top and legs in the correct position (X/Y) then move the table top in the Z direction the required height.  Not an elegant way to do it but it does work.

 Thanks  John,  I suppose  this is the way to " wing it "

Post the drawing so someone here can take a look at it and maybe figure out what's happening.

 My problem initially was when I align , my points  snapped on to the wrong soource and  destination points.  I have now figured it out  the way  I could get the correct snapping points  - is to  have 2 or 4 viewports  of the objects  and move them closer   and by using as you say 2d  commands  manually bring them to gether or get the correct snapping points to align them. 


Any way thanks  John once again  for getting my grey cells working