Portable Backstop
and
Scoreboard/Historical Display

These are what I use on the field or when setting up a
display of baseball history
The backstop is comprised of three 4'x8' sections of framed chicken
wire, lashed together with rope and steadied with four 5' long
sections of 1" electrical conduit driven about a foot into the ground
(one at each end and two where the sections are tied together).
 
This style of scoreboard might not be absolutely historically correct
(especially the Tally Bell), but it serves our purpose nicely.  On the
reverse side, doing double duty is the historical display that
includes a list of the differences between vintage and modern
baseball, original rules, a brief history of the game, various
illustrations, ball gloves and (handmade) baseballs from different
eras and an 1860 style base ball "under construction".     
.