De or het klapzitting?

The correct Dutch article is:

de klapzitting

Rule Words ending in -ing: almost always de. See the rule

How to use klapzitting

the klapzittingde klapzitting
this klapzittingdeze klapzitting
that klapzittingdie klapzitting
our klapzittingonze klapzitting
your klapzittingjouw klapzitting
every klapzittingelke klapzitting
which klapzitting?welke klapzitting?
a big klapzitting / the big klapzittingeen grote klapzitting, de grote klapzitting