I decided to try soil blocks for starting garden plants. Before I invested $$ in a soil block maker, I did a Google search on DIY soil blocks. This web page had the ideal solution for me. http://toppertwo.tripod.com/soil_blocks.htm I get my prescriptions mail order in 90-day quantities and use the containers for seed storage. I had two containers where one was slightly smaller in diameter than the other.
I used the bottom of the smaller container for the plunger. My containers were also taller than Toppers and I decided to take advantage of the increased length. I added a nylon nut to adjust the height of the blocks. I have read that you do not want to distort the taproot of carrots and parsnips. The additional length of the block will give me additional time to plant those plants in the garden.
The little brass acorn nut is for making the divot for the seed/s.
The divot is not evident, but it is there.