that happens regularly, that’s certain
[Dutch phrase of the week]
[dat is vas-te prik] 

When something is ‘vaste prik’ in Dutch it means that something happens with a certain regularity, or something happens so often and regularly that it has become a certainty. The phrase is also used in the form ‘[subject/topic] is vaste prik’.

The phrase apparently dates back to the practice of tax collectors to carry a stick that they punctured or made small cuts in to help them determine the amount of tax paid (as a counting aid). Such a stick is called ‘kerfstok’ in Dutch (for which I can’t find a translation).

Examples:
- “Op wie wachten we nu nog?” – “O, op Frank, dat is vaste prik met hem op vrijdag, dan is hij altijd te laat.” 
(“So who are we still waiting for?” – “Oh, for Frank, it’s always the same thing with him, on Fridays he’s late.”)

- “In het begin ging ik af en toe hardlopen in het weekend, maar nu is het inmiddels vaste prik.” 
(“At first I used to go running in the weekends every now and then, but by now it has become a habit.”)

- “Het is tegenwoordig vaste prik voor alle professionele atleten; na elke wedstrijd is er dopingcontrole.” 
(“Nowadays it is certain that professional athletes have to undergo a dope/drug test after a match/game.”)

- “Toeristen die niet uitkijken bij het oversteken, vaste prik in Amsterdam, vormen vaak een gevaar voor zichzelf.” 
(“Tourists who do not watch out when crossing the street, almost a given in Amsterdam, often pose a danger to themselves.”)

- “Voor Sheldon Cooper is pizza vaste prik op donderdagavond.” 
(“Thursday night is pizza night for Sheldon Cooper.”)

Related words:
- Prik: prick, prod, injection/inoculation [noun] [de prik, de prikken]. ‘Prik’ is also the Dutch word for ‘pop/fizz’.
- Prikken: to prod/puncture/pin, to inject/inoculate, to set/fix a date [verb] [prikte, geprikt].

Example:
- “Het is met werkende mensen altijd lastig om een datum te prikken.”
(“It is always difficult to fix a date with people who work / have jobs.” In this meaning of ‘prikken’ the verb is probably derived from marking a date on a calendar with a pin.)

- Frequent: frequent(ly) [adjective/adverb].
- Regelmatig: regular(ly) [adjective/adverb].
- Altijd: always [adverb].
- Zeker: certain, absolute(ly) [adjective/adverb].