During the installation of prefabricated wick drains (Prefabricated vertical drains) for soil consolidation you need some materials under the mandrel (lance) to hold the drain in the soil when you pull the mandril back.
So you have to use anchor plates or anchor rods.
Both is OK depending on site conditions.
I find the plate more easy to use.
When the mandril is pushed in the soil the plate holds the drain in the soil.