To prepare a horse for riding by equipping it with tack (harness, reins, saddle etc.)
2
To attach in a temporary fashion (with or as if with tacks or pins), as for example to fix pieces of fabric into position in preparation for sewing their seams, or to hang dropcloths as masking before painting.
"The stage ought to be here," said Miranda, glancing nervously at the tall clock for the twentieth time. "I guess everything's done. I've tacked up two thick towels back of her washstand and put a mat under her slop-jar; but children are awful hard on furniture. I expect we sha'n't know this house a year from now."1903, Kate Douglas Wiggin, Rebecca of Sunnybrook Farm:
Tack-ups serve for windows of miscellaneous shops, proprietors of these places being rewarded for their indulgence […]1916, Arthur Edwin Krows, Play Production in America, page 324:
They monogram napkins for department and specialty stores, print millions of cards and gift wrappings, design a wide variety of invitations, dance programs, decals and tack-ups.1953, Ebony, volume 9, page 48: