Used (at last) my DIY grid for vegetation cover estimates. I took an old stainless grid from a dish rack, marked intervals with nail polish (and taped on the corresponding numbers on the frame), and placed it on four plastic clothespins which hold onto electrodes I insert into the ground where I need them. The height is adjustable, within reason. The frame has to be tied to at least two diagonal 'poles', because it is easy to dislodge (I used shoelaces). Another electrode was my 'pin'. (I carry them in a plastic bottle, to better preserve my bag.)

So far it was workable for aboveground vegetation, and only a bit cumbersome to carry through dense undergrowth. However, when I began to map the underground part, it was a nuisance until you remove the soil (& nearly poked my eye out with an electrode - better to remove one pole.)

Why is this useful? Experienced botanists can estimate species cover with 10% accuracy (for abundant species). Inexperienced have to check themselves. So partly - for calibration. (You can have a group of students give their estimates, and then see how close they come; you don't even need to know the plants' names for this.) And it's fun, you can map rather small things if you have a notebook and a pensil and your grid is fine enough. If you don't have calibrated paper, just write the numbers as xy coordinates.