Ronald Wallace's poem "Building an Outhouse" creates an extended simile by comparing the construction of an outhouse to that of the construction of a poem.
A poet needs to be concerned with the same things that a builder needs to be concerned with. Wallace creates the simile by stating the comparison in the first line:
It is not unlike building a poem
Wallace then goes into the concerns that a builder would have when constructing an outhouse. The concerns lie in the shape, the materials needed, and the tools needed to construct an outhouse. This is comparable to the tools, shape, and material needed to construct a poem.
If the shape of an outhouse is not correct, it can throw off the balance of the structure. This is true of a poem as well. If a poem does not have balance, it can throw off the underlying meaning for the reader.
If the tools used to create an outhouse are broken or wrong for the project, the building will suffer. Again, this is the same for a poem. If the tools used (figurative language, form, or theme) are wrong for the poem, the poem will suffer.
Lastly, if the materials needed to build the outhouse are tainted or bad, the structure will be unable to withstand time. A poem is typically written to survive- no author wishes to put out the mental and physical energy in constructing a poem to have it collapse upon itself. The material needs to be able to survive.
In the end, Wallace admits that only a good outhouse and, therefore, a good poem are capable of lasting forever. He ends the poem with the following line, begging critics to sit upon his creation:
Though the critics come sit on it, and sit on it.
Wallace knows that any text, or building, is subject to criticism. It is only through the use of good tools, materials, and shape which allows a person to "sit on it".