Question: There are two meshes that are clipping into each other.

![enter image description here](https://i.stack.imgur.com/oaV8c.png)

I used the boolean modifier to subtract the cylinder from the wall object. How do I fix this problem?

**[.blend file](http://www.pasteall.org/blend/33511)**

Answer: 
If you are referring to what can be seen in the image below, this is called z-fighting. It is when to surfaces overlap and are in the same 3d space. This is not physically possible in the real world. 

![enter image description here](https://i.stack.imgur.com/7gpX1.gif)

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To fix this you would have to get rid of one of the overlapping surfaces. 

1. Select the object `Cube`
2. Select the faces that are overlapping.

![enter image description here](https://i.stack.imgur.com/lEmQV.png)

3. Delete them, `x` -> *Faces*

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**Final Result**

![enter image description here](https://i.stack.imgur.com/dSRwK.gif)
Comrade's answer is good. If you want to keep both meshes intact, there is an alternative way.

1. Select the `Cylinder.001` object
2. Scale the object by hitting `s`
3. Scale it down by an appropriate amount. You can try `.99` to start. Keep adding 9's until you see z-fighting happening again. If so, hit the backspace to erase the last digit.