Some of you have probably used this technique but here it is for those that have never seen it.
In case the router or switch doesn't come with a mounting template, or you got one second hand, try this trick to figure out where the screws need to go to mount it to the wall.
Put the device on the table so that the mounting holes are facing up,
then take a piece of paper and mark "UP" on it for some orientation of how you want to mount it.
take a pencil and use the side of the lead to rub across the paper in the area where the mount holes are.

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It should look like this

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Put the paper where you want it on the wall and drive the screws through the top of the transferred pattern.
tear the paper out of the way and mount the device.

Cheers!
In case the router or switch doesn't come with a mounting template, or you got one second hand, try this trick to figure out where the screws need to go to mount it to the wall.
Put the device on the table so that the mounting holes are facing up,
then take a piece of paper and mark "UP" on it for some orientation of how you want to mount it.
take a pencil and use the side of the lead to rub across the paper in the area where the mount holes are.

-----------------------------------------
It should look like this

------------------------------------------
Put the paper where you want it on the wall and drive the screws through the top of the transferred pattern.
tear the paper out of the way and mount the device.

Cheers!