You can unlock and make a Ladder in ACNH by using DIY Crafting. With this tool you can gather materials.
How To Get Ladder in ACNH
You can craft a Ladder by using 4x Wood, 4x Hardwood, 4x Softwood materials. You unlock the DIY Recipe from Tom Nook after placing 2nd house plot.
|Recipe||Materials Needed||Obtained From|
|Tom Nook after placing 2nd house plot|