How did people invent the first straight object without a different straight object for reference
-
-
I used both of these while working with carpenters on bridge work.
Thanks. Twitter will use this to make your timeline better. UndoUndo
-
-
-
a chalk line is a string pulled taught between two points a plumb bob is a string pulled taught between one point
Thanks. Twitter will use this to make your timeline better. UndoUndo
-
-
-
Thanks. Twitter will use this to make your timeline better. UndoUndo
-
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.