
(as in an indoor TV antenna, camera tripod)
Jammed. If the metal has been dented, try to straighten the dent by inserting a metal rod, heavy wire or wood dowel up inside the tube. Or you can try to squeeze out the dent with pliers wrapped with adhesive tape to prevent scarring of the metal. But either job is very difficult and success is highly uncertain.
If the tubes are jammed by corrosion, saturate trie joints with Liquid Wrench penetrating oil.
Bent. If you want the tubes to telescope, your only hope is to work out the bend by inserting a metal rod, etc., as above.