Bailers are used for cleaning out wells or getting samples from downhole solids. There may occure sand, rust, scale or other unwanted materials which could prevent other tools from getting down. That’s when the bailer comes in use, this could possibly clean out the sand or other material from the well, if it’s not to solid.
There are several different bailers, for example:
Stroke(pump) bailer, hydrostatic bailer, sample bailer, jet bailer.