I get asked this question a lot from engineers & retail customers so i wrote this short guide, let me know if you think any part could be worded better but it makes sense to me!:
Firstly check which corners set is required on this list. If your phone isnt listed i often find the standard corners that come on the cradle are fine (Corners ‘F’ I believe).
Next ensure that the top of the cradle is in the locked down position as per below:
Then use the end of the Micro USB lead to press in and lock in the 3 locking tabs (Top, bottom & right hand side)
To this recessed position….
Insert the phone and adjust the height & width of the corners to fit the phone, once fitted press all 3 locking tabs again to lock it in that position. You will find a selection of different corners are supplied with the cradle, in my experience it’s quite rare to need them usually the default ones fit most models. The corners can be extended with a thumb screw if you need a little extra depth to allow for a phone case etc.
Press the large release button to remove the phone.