V-block design is very important to the utility of the tool. A proper V-block like the one in the center in the photo has bolt-on, low-profile clamps that won't interfere with the milling machine or drill press chuck. Moreover, the clamps remain inboard of the sides so the block can be laid on its side with the workpiece still clamped as would be required if drilling orthogonal holes.
The less expensive block on the left is more commonly seen. It can't be laid on its side and the tall clamp interferes with everything. There isn't much one can do about laying it over but the obstructing clamp can be fixed. Shown in front is one of a pair of clamps I made; the other is shown mounted on the block on the right. Note the use of brass hold-down screws to prevent marring the workpiece.