Hi Loganka,

> I'm not sure if I didn't understand what he means or if I did understand but it
> doen't work because i did something wrong before..

So I think that step means to select the edges around your hole, like for example make a selection like this on your model that you posted:



Then run the Construct > Extrude command, which will punch out those edges into a surface along one straight direction. By default the direction will be along a world x, y, or z axis direction like this:


That will work fine for your top one but for the side ones where you want it to go along a 45 degree angle, you will need to push the "Set dir" option in Extrude:



Once you push "Set dir" in Extrude, that then asks you to pick 2 points and the extrusion direction will go on the line between those 2 points. So to get the extrusion to go at a 45 degree angle you would want to switch to the Front view, pick the first point at the origin snap and the second point anywhere along a 45 degree angle line from the origin. You can use angle constraint to get an exact 45 degree angle by typing in <45 and push enter right before you pick the second point. That will enable a one shot angle constraint of 45 degrees so that straight snap will go in 45 degree increments for that one pick rather than the regular default 90 degrees. Or if you are going to be doing a lot of 45 degree angle things, you can change the default straight snap to 45 degrees under Options> Snaps > Straight snap options > Snap angle.

Once you pick the 2 points you will then be back in the extrude distance stage and you can enter in a distance or pick a point with the mouse and your mouse will track along that newly defined direction line.

Once you have built an extrusion in this way you then select the extrusion and the main body and use Edit > join to glue them togeher.

Hope this helps!

- Michael