Hi, take a look at this screenshot:
I want to make that selected face 78" tall, without distorting the proportions of the whole object.
Could someone tell me how to do that please. (Yes I am noob :D)
Edit: Basically I have modeled this object in perfect proportion, but now I need to get it at the right size. I know that face I have selected is 78" tall, so if I can get that face to that length, the whole thing should be sized correctly.
I would just model the face in the right proportion and then model the rest of the mesh from that piece, as it looks like its a very simple model, it would only take a few minutes.
But if you want another way then do this -
If you select the part you want to scale, you can choose to scale along a specific axis. I.e pressing S and then Z will scale the selection on just the z axis.
You can also get more control by scaling from a selected vert, face or edge. so if you selected all the mesh, and made one of the very bottom verts the active selection. you can choose to make transforms from that location, so scaling up in the Z axis with the bottom vert selected would scale the mesh upwards from that location, rather than scaling from it’s centre point which would case the top and bottom of the mesh to be scaled away from eachother… meaning the bottom would go downwards rather than it being scaled from its base point.
To make transformations from selected points, use this set of options (Highlighted in the attached image below)
You can also transform from origin, individual origins and the 3d cursor 
makes modelling a lot easier to control.
Also, if you wanted to scale that face on it’s own, with no other parts of the mesh effected,
Then select the face and press Y. This will split the face from the rest of the mesh. disconnecting its verts so you can transform the isolated face.
If you wanted the face to be a seperate object when editing it, select the face and press P, then click the option “Selected”. this makes that face its own object. you can then edit the face and when you are happy with the proportions, you can join it back to the original object by going into object mode, selecting the face object and then also selecting the original object and pressing Ctrl+J
Thank you for the help. My “model” is now the right size 
