Theory:

The poem "The Shed" by Frank Flynn deals with the speaker's desire to visit the shed in his garden. The shed is not adequately maintained, and hence, is filled with spider's web. The hinges of the door had become rusty, and as a result, it creaks as the wind passes. The speaker listens to the sound as he lay in his bed and expresses his desire to open the door one day.
 
In the second stanza, he talks about a window on one of its walls. It is, as expected, dusty and old. Moreover, three panes of its glass have cracked. Each time he passes by the window, he is overcome by a feeling that someone is watching him from the shed. The speaker then wishes that he could at least peep through the window and see what lies inside.
 
In the third stanza, the speaker reveals how his brother had scared him into believing that there is a ghost hiding under its floorboards. The speaker then hopes that he could, at the minimum, take a peek at the shed from a safer distance.
 
Later, in the fourth stanza, he convinces himself by rejecting all his above fears, such as the ghost, spider, and the noise as groundless. The speaker is determined to visit the shed; however, he concludes by stating that he is not ready to do so yet.