You can buy one for about $200, or make one for almost nothing...if your doing POTA or a portable operation, anywhere this will support your mast...
Here’s a simple, inexpensive drive-on mast support that I have been using for more than ten years now. It’s been particularly handy for quick trips to the field, such as National Parks on the Air (NPOTA) activations.
"[This is an updated description of the drive-on antenna support that I have been using for many years. This version originally appeared in the July 2016 edition of QRP Quarterly in the “Idea Exchange” column and most-recently in the October 2024 edition of Radio ZS, The Journal of the South African Radio League. You can still find the older article here. A revised, “step-by-step” version appeared in ARRL’s On the Air Magazine (May/June 2024 edition). ]"