Guide for head restraint without pushbutton:

Release catches (1) and slide guide (2) upwards.

Fig 1: Releasing catches

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Pull guide (1) out of backrest (2).

Fig 2: Pulling Guide Out Of Backrest

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Installation: 

1. Catch (1) on guide (2) must not be damaged.
Fig 3: Checking Guide
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2. After installing guide (2), make sure it is properly seated.