Complete set of 12 shapes formed by this puzzle's black squares

Question:

Answer:

PENTOMINOES

Length:

Similar Crossword Questions:

Row of black squares preceding or following six puzzle answers, thereby completing them
Web concerns ... and based on six familiar names hidden in rows 1, 4, 12 and 15 of this puzzle grid, what the black squares in those rows symbolize
How this puzzle's black squares are arranged
Like aleph in the central black squares of this puzzle's grid
On hold ... or what the seven rows of black squares in this puzzle's grid spell in Morse code
Trains, in a way, and the key to 18 of this puzzle's black squares. (Ones that begin with the keyword are asterisked. The others are for you to discover.)
Common interface that is a model for several squares in this puzzle
What's revealed by connecting the special squares in this puzzle in order
What spouse does, step 4 [hint: look at the black squares of the grid]
Landmark inaugurated 3/31/1889 whose shape is suggested by nine squares in this puzzle's completed grid
Company whose movies, not counting sequels, are all included in this puzzle [Circled Squares: 2009]
Octet of black squares in the middle of this grid, typographically
Fans of black-and-white squares
Where GIs fought Charlie[LAST WEEK: "Lady X" was Ingrid Bergman, whose first name is revealed in the circled squares (IN + GRID). Seven of her one-word movie titles can be seen "straddling" black squa
What black and white squares do on a chessboard
Lower pair of black squares in this grid, typographically
Question asked by a customs officer or a kid on Christmas ... with a hint to this puzzle's circled squares
Company "sorted" in this puzzle's circled squares
Welcome mat spot (our puzzle title hints at the theme revealed by the pattern of circled squares)
Black Friday destination found in nine of this puzzle's Across answers
Number of times this puzzle's theme word appears diagonally in the grid (to complete the puzzle, shade those words plus the Down answers that begin where they meet)
Words of reproach, and a hint to how the four longest puzzle answers are formed
Economic term named the 2011 Word of the Year by the Oxford English Dictionary...and a description of 6 squares in this puzzle
Lower septet of black squares in this grid, typographically
Nonet of black squares in this grid, typographically