Hi @PatriotOGrady . L can be, for example, a 1x (p+1) row vector, and B is a (p+1) x 1 column vector. In a multiple regression setting, B would be a column vector with elements B0, B1, B2, …, Bp. This is the case for example where Y= B0 + B1*x1 + B2*x2 + …+ Bp*xp. And, for example, if you are testing H0: B2=0, then L is a row vector <0, 0, 1, 0, …, 0>. This results in LB= B2.
For the whole model test, L is a p x (p+1) matrix (each row similar to the row vector described above with all zeros except a “1” in the appropriate position) resulting in, effectively, H0: B1=B2=…=Bp=0.
You may want to review the Gauss-Markov model and the associated matrix/vector representations and operations.