[DutchmenSport]

If on asphalt, I usually do not put anything under the tires, unless the site is unlevel left-to-right (side-to-side). Then I'll put the appropriate height of lumber under the low side of the trailer to level it more. However, I do use blocks of wood under the jacks (all 6 of them) for a couple reasons. First, putting blocks under the jacks means the jacks don't have to extend as far. No danger of stroking out, and the jacks are more stable at a shorter length. Second, all the weight of the trailer on the jack foot pads, because of their small foot-print, will indent the asphalt.

I park my Montana at home on our asphalt drive way. I park it in exactly the same spot all the time. I have boards set up in the drive way (because it's sloped left-to-right for water drainage when it rains), one side of the trailer sits over 2 inches lower than the other. So, the low side is on 8 foot long treated lumber, stacked 2 high.

I also ALWAYS use 4x6 inch posts under the jacks. We had our drive way completely resurfaced with 4 inches of additional asphalt about 3 years ago. After the trailer was sitting there, within the first 6 weeks, the weight of the trailer was causing the asphalt to indent under those blocks and under that 8 foot long board. After 3 years, I've had to add an additional board because the first (or bottom) board has sunk into the asphalt over an inch (yes... 8 feet long), and those blocks under the jacks I am now turning them, not parallel to the length of the trailer, but perpeindicular. They've left indentation in the asphalt and sunk the asphalt enough, there are holes now about an inch deep everywhere.

If it was not for the wood spreading out the weight, I'd probably have 2 or 3 inch deep holes in the asphalt now.

If the asphalt under your trailer is not yours, then you probably don't care if you leave indentations when you leave the site. But if you care about the campground you are visiting and want to feel good about it when you leave, then put some lumber under your tires so the next person won't have holes to deal with.