I claim the ornamental design for a studrail, as shown and described.
FIG. 1 is a side perspective view of a studrail.
FIG. 2 is a side view of the studrail.
FIG. 3 is a side view of the studrail from a zero degree reference.
FIG. 4 is a side view of the studrail from a 45 degree reference relative to FIG. 3.
FIG. 5 is a side view of the studrail from a 90 degree reference relative to FIG. 3.
FIG. 6 is a bottom view of the studrail with the shaft showing.
FIG. 7 is a top view of the studrail with the shaft hidden; and,
FIG. 8 is perspective view of four studrails connected to a base member.
The broken lines in FIGS. 1-8 illustrate portions of the studrail that form no part of the claimed design. The additional broken lines shown in FIG. 8 illustrate environment and form no part of the claimed design.