What tool can be used to initially check coupling alignment?

A straight edge is an effective tool for initially checking coupling alignment because it can be placed alongside or across the two shafts being aligned. By using a straight edge, you can easily identify any gaps or misalignments between the coupling halves. A straight edge provides a visual cue that highlights misalignment due to the level of contact or the presence of space, which helps in determining whether adjustments are needed.

In contrast, while a ruler or measuring tape can measure distances, they may not effectively indicate alignment issues since they do not provide a continuous surface for comparison. A level can help ensure that a particular component is plumb or level, but it does not directly assess the alignment of couplings. Therefore, the use of a straight edge stands out as the preferred method for the initial assessment of coupling alignment.