Attachments & Particle System UI
Attachments are points on your model where you can attach extra models and particle systems (guns, sprites, etc). This page details both Attachments and Particle Systems since the Particle System controls are also in the attachment rollout.
OSL: Swirl

OSL Swirl is a simple texture map with a few controls on making swirl textures or swirl masks.
Random Elements
Random Elements Modifier lets you randomize position, rotation and scale of geometry or UVs at the element level.
Grouped Geometry is Not Supported
When exporting grouped models to SMD, the SMD exporter will fail to export your model correctly.
Alpha Spec
This utility is a helper function to convert your Specular Level bitmap into the Alpha channel of another bitmap.
BSP Topics
Basic discussion of BSP, VBSP and compiling topics.