Making proper arches

There are many ways to create arches in the goldsrc engine. But the method which saves the most polygons wins. I have been mapping for quite some time now and I have seen many mappers make arches poorly. They could have saved a lot of polygons if they would have carefully made their arches. So I am going to explain this tutorial in detail.
 In this tutorial I will teach you how to create arches the proper way in cs 1.6

Step 1
First, make a 128x128 wall. This is the base brush. From this, you are going to create a arch. Now, clip the sides of the brush by 16 units. It will look like this:

Now, create a cylinder of 96x96x96 units and place it next to the middle portion of the wall. This ensures it fits properly in the middle of the wall. It should look like this:

Step 2
Resize the wall behind the cylinder until its height is half of the cylinder. Now select the wall and use the clip tool to cut segments in the wall. Cut segments for every side of the cylinder. See this screenshot:

My cylinder is composed of eight sides so the wall is divided into only four segments. If your cylinder is made up of more sides, lower the grid size and cut more pieces. There is no need to match the exact location of the vertice on the cylinder but you may need to use smaller values to create more detailed arches.

Step 3
After cutting it, move the vertices upwards to match the vertices on the cylinder. There is no need to match the exact vertices but you may need to do so if you want to create detailed arches.

 You should get a alert box asking you to merge the vertices at the center. Click on yes. Now refer this screenshot:

Move the vertices on the blue circles to the orange circles. This makes them triangles thereby reducing their polycount. This technique saves a lot of vertices and shows a lot of difference when lots of complex arches are used in a map. When making complex arches, move all the vertices on the orange circle. You will get multiple alerts asking you to merge. Click on yes. Now delete the cylinder. The final arch looks like this:

Notes
To makes arches quickly, simple make one side and then copy paste it and rotate it to 180 degrees and place it next to the other arch.
Making cylinders of 32 or more sides may not allow the map to compile. To overcome this problem, simply make a 32 sided cylinder and cut it in half. The compiler will treat it as two separate brushes.