Sorry about the cross-posting.
I used to own what I call 'support posts'. 30 years ago I bought them at
Sears. They are telescoping 3"± tubes with an acme jack screw on top. Used
for either temporary or permanent support of sagging floors etc. Mine would
telescope from about 5 feet to 8 feet ±. Need to buy some since I am
digging a basement under my house. Can't for the life of me remember what
they are called, and therefore can not find any on the web or elsewhere.
I've searched under 'jack post', 'house jack', 'support post' etc.
All help appreciated.