A tool that toggles a special no-zoom crosshair, which is available for all sniper weapons in Counter-Strike 1.6. This will help you to aim with snipers, when perfoming quick scopes or no scopes.
Basically, this tool has a bunch of sniper models with crosshairs, which replace the game's ones. The tool does not inject the models, but simply copy and paste them.
The reason you would need to change the models back and forth lies in competitive gaming. If you're playing in competitions, you have to play with default models for your weapons. Crosshair models might ban you from these competitions. Yet, (most) public steam and non-steam servers will not ban you for those.