The ornamental design for a toybuildingblock, as shown and described.
FIG. 1 shows a top and side perspective view of the toy building block.
FIG. 2 shows a bottom and side perspective view thereof.
FIG. 3 shows first elevation view thereof, the opposite site being a mirror image thereof.
FIG. 4 shows a second elevation view thereof, the opposite site being a mirror image thereof.
FIG. 5 shows a top plan view thereof.
FIG. 6 shows a bottom plan view thereof, the dotted lines represent the bounds of the claim which form no part of the claimed design; and,
FIG. 7 shows the toy building block connecting a plurality of additional toy building blocks, the dotted lines representing the environment in which the article resides and forms no part of the claimed design.
The broken away symbols in the drawings indicate the appearance of any portion of the article between the break lines forms no part of the claimed design.