The pipes have screw caps in both ends. I open one end, fill the pipe with bundles to be soaked and cap the pipe again. Each pipe has a 5cm hole for filling it with water using my garden watering can and for emptying it again siphoning with a thin hose.
This has worked well except for the fact that the pipes are too small if I want to soak willow for more than one project. I really regret that I didn't invest in larger pipes as it can be a little tricky to get the bundles in and out when I stuff as much as possible in there.
This summer my resourceful husband made me a new, very flexible soaking facility.