In Shōbōgenzō Jinzū, Zen Master Dogen discusses "the state in which, facing all existent and non-existent dharmas, the eyes, ears, nose and tongue are each untainted by greed. Not to be tainted by greed is untaintedness. Untaintedness is the everyday mind and is the state of 'I am always sharp at this concrete place'."
Like much of Dogen's writing, this needs to be chewed on for a while before it can be digested. The first symptom of Ummon's first sickness is when things are not yet clear and something appears before you. The "sickness" here is the delusion of separation of self from the appearance. If "something" appears before "you," you've already divided the nameless, formless substance of the universe into "you" and that "something," missing entirely the seamless, interconnected nature of reality. Yet, shrouded in our delusion, we cling to the name and form of the appearance and to the egocentric concept of self identity.
Dogen is discussing the healthy state free from Ummon's first sickness. Things still appear before the awakened mind, but when it is facing an existent dharma or even a non-existent dharma (such as a thought, a concept, or an emotion), the awakened mind is not tainted by attachment to the senses. Recognizing that all sensory sensations are like a dream, the awakened mind does not cling to the delusion that the perceptions are real or that they are not all aspects of the one thing. This untainted mind is in accord with the Buddha way, and one with such a mind once remarked. "I am always sharp at this concrete place."
In the Rev. Hubert Nearman's translation of Shōbōgenzō Jinzū, the same passage discusses "eyes, ears, nose, and tongue all being undefiled by the various material and immaterial things that arise. ‘Being undefiled’ means ‘not being stained with desires’. ‘Not being stained with desires’ refers to our everyday mind: it is our continually cutting through whatever arises here and now."
So in the statement "I am always sharp at this concrete place," "always" means "continually" and "this concrete place" means "here and now," wherever and whenever that might be. "Always sharp" means cutting through the appearance of whatever arises. "I am always sharp at this concrete place" means the everyday mind of Zen that continually cuts through whatever arises here and now.
Okay, can you use it in a sentence?
A monastic once asked Zen Master Tozan, "Among the three bodies, which one does not fall into any category?" Tozan replied, "I am always sharp at this concrete place."