To enable collision for a 3D model in Roblox, set the **CanCollide** property of its individual parts to "true" (models themselves don’t have collision—parts do) and use **Collision Groups** for custom collision rules.
Roblox’s collision system works at the part level, so every part in the model (e.g., a table’s legs or top) needs CanCollide enabled to block players or other objects. Collision Groups let you define which groups collide—like making players hit a door but not a wall decoration.
If parts aren’t colliding as expected, double-check CanCollide is on for all relevant parts and Collision Groups aren’t ignoring each other. For quick edits, select multiple parts in the model and adjust CanCollide in the Properties panel at once.