This is the 14434th most frequent German word.
klotzen
To work hard or put in immense effort.
Here, 'klotzt' is used colloquially to mean to put in a lot of effort and determination.
Er hat beim Laufen richtig geklotzt, um das Rennen zu gewinnen.
He really worked hard while running to win the race.
In this case, 'Klotze' (plural of 'Klotz') refers to large blocks, specifically concrete ones in this context.
Wegen der Bauarbeiten haben sie an der Ecke große Betonklötze hingestellt.
Due to the construction work, they placed large concrete blocks at the corner.
Here, 'klotzt' pertains to the action of shaping or modifying a piece of wood.