Need a little help extruding a mesh please

I have created a 3d map with as a mesh so it’ll highlight the bridges much better than outlines. I have extruded the mesh down by 2mm but i didn’t know the extrusions would be hollow. Is there any way to fill these in so they are solid, or even better would be if i could just extrude them as a solid to begin with. I am a beginner with Rhino but i have experience with F360.

cadmapper-dublin-leinster-ie.3dm (5.0 MB)

Hi Rich - what command are you using? ExtrudeMesh or Guimball- extrude or? Here I get solids from both of those.


Hi Pascal. This is my first time ever using a mesh in Rhino and, like i said, i’m already a beginner as it is, lol. Anyway, i was using ExtrudeMesh but i tried the gumball-extrude but that command doesn’t seem to be available for me…? Basically, when i typed it in, it wasn’t in the list of available commands.
Fo a little context, it’s specifically the bridges going across the river running through the city. Here is a cleaner version of the file where i’ve only edited the parks and water layers. It’ll be easier for you to see the actual pieces i need help with as i think i screwed up the previous upload.
cadmapper-dublin-leinster-ie.3dm (10.5 MB)

Hi Rich - these meshes look like they are collapsed from closed 3d meshes - if you Explode one and just extrude one of the parts, it will work -


Pascal, thank you for your advice. There is some really fucked up geometry in that map so i decided to redownload it with the outlines instead of the meshes and since it was less than 1sq km i was able to select all of the outlines and extrude them which essentially did exactly what i wanted and did every single road/bridge in 1 go instead of me arguing with my PC for the next few hours, lol.
I really appreciate your help my friend.