The problem is that in the tutorial he doesn't extrude, he just translates it. Instead of hitting E to extrude, just hit G to grab, then Z to limit it to the $Z$ axis.
Or you can always click the icon for Move, which is the third one down on the left, then use the vertical blue Z axis arrow to move those vertices.
There are two things to prevent those transparent faces.
For Cycles - add some thicknes to the whole wall, before extruding individual parts
For Eevee - Set material Blend Mode to Opaque
Cycles - add thickness before extruding. Just extrude the whole plane first.
Eevee - set blend mode to Opaque
You can start considering the object symmetries, 8 parts like that:
Thus, we'll try to make it and use Blender's mirror modifier.
As rounded parts are generally more complex to do, we start with them:
Add a circle, with a relative low resolution (say 16 vertices). This will be the center of the shape.
Then duplicate it in edit mode ShiftD and extrude and ...
seems vert and edge selection was being extruded too, so they needed to be cleared with bpy.ops.mesh.select_all(action='DESELECT'), and mode_set flips to update mesh's selection, and then extrusion result:
epsilon = 1e-04
mesh = box.data
polygons = mesh.polygons
for c in [c1,c2]:
for i in [0,1,2]:
Add a mesh of the cutout(orange piece), enter it in the place want to be cut out, add a boolean modifier to the main mesh(letter),(its already at difference from default), click the eyedropper and select the mesh cutout(orange), apply the modifier and move away the mesh cutout(orange) to get a result you want.
Maybe, instead of the native curve bevel, you can use Array and Curve modifiers on a profile segment ..(blue section, below)
The array can have 'Start' and 'End' caps (red and yellow). It's easier to use Constant Offset in the array. Adjust (here, in Z,) the positions of the caps in Edit Mode, until the 'Merge' in the array takes, before giving the array ...
For some reason I thought modifiers were the "next generation" geometry tab.
Luckily it turns out I had overlooked that the geometry tab still exists in Blender 2.8!
It's the green triangle icon in the menu on the right hand side of the default layout.
From there on, it's just like in Blender 2.7, as I described in the question.
Thanks for the quick ...
Add a cylinder object in object mode.
Select the base mesh and goto modifier stack and select "Boolean Modifier".
Select the cylinder mesh in the boolean modifier settings. Hit Apply.
Now, delete the unwanted cylinder object.
Select the base mesh and goto Edit Mode TAB
Select the vertices of the formed circle and E and Hit Z to Extrude the vertices in Z-...
It would be best to plan nice topology from the beginning. You can form the 'pill' shape with a circle, splitting(Y) it's half, moving it and filling everything(F), if you then inset(i) the resulting face, you get the geometry that you can use to re-form a circle by snapping half of it back to place(hold Ctrl down while in transform operation to temporarily ...
By saying extrude along a path, are you referring to 'Skinning'? If so, they have to be separate objects, then you use one as a 'Bevel' object to skin(bevel) the path. If you could post a screen shot and clarify this, it would help.
You could make your extrusion mechanically, as you have, but to 0 height, make a vertex group from the extruded vertices, and aim a Displace modifier at it, followed by a Weld to disappear it when you set the displacement to 0.
Advantages over the Boolean given by @person ? Not many.. unless the Boolean is playing up because of necessarily coincident faces
You can add a groove using a boolean modifier.
My process would be as follows:
Duplicate some faces from your original, then separate them into another object.
Scale them down, and extrude out some thickness to get the inverse of the groove you want:
Add a boolean modifier on the first object set to difference, and select the new object as the target: