What are you aiming to achieve?

Do you want to intersect a stanchion to a baseplate/foundation, and then the fdn/bplt to a deck or slab or floor?

Do you want to simulate T and I stiffeners run along an inner shell plate?

Do you want to drill a hole through a pipe or plating to simulate lightening holes or rat holes?

Many of those efforts can be as simple as creating planes or discs using 2 parallel lines with a surface between them, or by using a circle with a surface made from the "Cover Surface" tool to cut or Boolean other objects.

Angle irons or sideshell or plate stiffeners can be created bt creating a web and a flange and then using the "One Rail Sweep" tool to sweep the surfaces, which then can be thickened. Some csn be adjusted in thickness even after reopening the file.

To create sideshell stiffener curves that can be moved later without recreating each surface and dependent solid, use the "Project Curve Surface" tool on a line that represents the thrown line. But, do it with the Ctrl key, so you can embed the curve (which will become a spline) intomthe surface. Then, if you longitudinally slide the guide line or parent line for, say, a sideshell stiffener or stud in a house wall, the spline that moves causes any dependant/dependent lines to move, causing simultaneous moving of associated surfaces, which causes movement of associated solids.

If you have the trial or activated VCP 7 or 8 or Shark LT v 8, play with the "Push-Pull" tool. For example, creat, in plan view, several overlapping circles, some hexagons, etc. Then.via the PP tool, hover the mouse pointer over an intersected out non set area. Click it ONCE, then let go of the mouse. Hit your preselected key to get into an ortho view, then use the Tab key to get the cursor into the input field to tell VCP or Shark to what distance to move or raise (do not confuse with "elevate surface") the surface. It raises as a solid, ehich you can later hollow out via the "Shell" tool. You can thn make a city that way.

If you want to make a topography of a landscape, creat an area of surface to encompass you play city. Then, use the relevant tool to add control points tomthat surface. Then, in a convenient view, raise and lower control points singly or randomly to creat contours of the "terrain" you are after.

Have fun!