2000 ml320 headlights
 

Hello
I have searched and cannot find an answer to my problem.
When we bought the 2000 ml320 I noticed the headlight buld covers were missing on both sides.
I bought new covers and can not get them to snap into place.
Is there a trick to this or do they need a special tool?
I have worked on cars and bikes for over 50 years and have never seen anything like this.
Thanks for any help Dan