In this tutorial i am going to show you how to start the editor (hammer) and some basic functions that hammer uses

Starting Hammer

Select the Tools Tab in Steam and launch "Source SDK"

In the Source SDK window, do the following

Change the Engine Version to "Left 4 Dead"

Change the Current Game to "Left 4 Dead"

Double-click on the Application "Hammer Editor" 

Once Hammer is loaded, you can start a new level by clicking on File > New

Four editing windows should appear.

Note: If your viewports are not equally sized as in the image above, you can resize them by going to View > Autosize 4 Views.

Below are some of the basic functions of hammer have been explained

Hammer Editor Basics

UI Layout: 

Tool Bar

The Tool Bar switches to different modes that allow you to select, place entities, build brushes, texture, etc.

Select Box

The Select Box switches between modes of selecting

• Groups – you will select the whole group of objects if you select one of the children
• Objects – you will select an entire object even if it consists of more than 1 brush
• Solids – you will select each brush separately even if it has been joined with other brushes to make one object

The Texture Box

The Texture Box allows you to see the current selected texture and to browse for other textures by going into the Browse… Button.

The Entity Box

Entities are the various things that you can place in your level that are not brushes. While brushes are the basic building blocks of levels, entities are pretty much everything else. You can place lights, props and items using the Entity Box.

The VisGroup Box

VisGroups are a way to organize your level. You can place both brushes and entities into VisGroups and label them so that you can hide them or reveal them. This allows you to see what you're working on in a much cleaner way than leaving everything visible.

That's it for this tutorial, hope it helps

Welshy

Source http://www.l4d.com/LevelDesignDocs.zip and revmonkey1977