Western Sahara-into-Mauritania Border Crossing
Visa
If you did not know already, you get your first heartattack right as you step your foot into Mauritania: since February 2015, the fee for the Mauritania visa is 120 euros, double the amount than before. It is possible however to obtain the visa at the border (at least some border posts, but, as of 2015, not all of them).
Laissez passer
In order to get the 'laissez passer' for your car, If you allow 'the fixer' to prepare your documents to present to the gendarme, he will ask you for 50 euros for his 10 minute work. The gendarme will not take any money from you for the 'laissez passer'. You are not required to pay for this document, but the gendarme will tell you you should pay to the 'fixer/helper'. The fixer will get very agressive if you don't pay him. He will even take the document from your hands, if you let him.
It is highly advisable that you do not hand any of your documents to anybody but the gendarmes. If you give your documents to somebody without uniform (no matter how well dressed he is and how comfortably he walks around the different offices), you will end up paying something. It is important to note the gendarmes will not take any money from you to issue the 'laissez passer', but they will tell you to pay something to the fixer. Clearly, they may get in trouble if they take any money directly from you, but, obviously, they will get some of your money from the fixer.
Car insurance:
Mauritania also requires you buy an insurance for the visitor's vehicle. At the border, you will be asked for 25-30 euros for one month of insurance.
As you approach the Senegalese border, when you explain at the checkpoints you are heading towards Senegal, you will be offered help to smoothly go through the border. We were repeatedly given the contact information of Mr. Mohamed Ali. Supposedly, he would help us at the Djalma border crossing. Then we found out Mr. Ali will get us a car insurance for Senegal. They will insist there is some problem at the Senegalese side and it will become impossible to get an insurance once we are there. Do not do it. You can be sure there will be no problem to sign some insurance in Senegal. Most certainly, the Senegalese will be waiting for you and be also very excited to rip you off on that one as well. At least, the car insurance you get in Senegal, although not very useful, will most likely be valid in Senegal.
