I came across this table in EHLL:
Table 1: Past, present, future, imperative, and infinitive forms
Sadan, T. (2013). Verbal System: Modern Hebrew. In G. Khan (Ed.), Encyclopedia of Hebrew Language and Linguistics (Vol. 3, p. 927). Brill.
At first I thought it is some sort of font problem. The book does not explain it, but after a number of seconds I understood that the squares are slots for the verb root. Someone else may be better in explaining it.
