The round up of Jews in a large scale started in Rotterdam in June 1942. One was summoned to report for the provision of additional work in Germany in Westerbork to be medical examined and one had to appear 30 July 1942 at 18.00 hours at the rallying point Rotterdam, at Entrepotstraat in Loods 24. In the first instance it involved just people up to 40 years of age. For the first transport, aproximately 2000 people were called up. Those, who worked for the Jewish Council, medical staff and the sick were exempted . Of the 2000 persons who were summoned, 1120 appeared. (the Jewish Council was expanded those days rapidly, to save more people from deportations).
Source: website Joods Erfgoed Rotterdam.
Addition
Summons in Rotterdam for provision of additional work in Germany.