I learned this convention from a friend in NC about 15 years ago. It uses 2d and 2h as opening bids to describe a 4-4-4-1 shape. The 11-15HCP any 4-4-4-1 ROMAN always got me in trouble.

2d= 4-4 or 5-4 in the minors a 4 card major and 12-17 HCP. The only forcing bid is 2nt. With 12-14hcp opener rebids clubs to show 4 hearts and diamonds to show 4 spades. With 15-17 HCP bid the major. If responder bids hearts and that is not yours you bid spades partner may pass or correct to a minor.

2h = 4-4 in the majors and a 4 or 5 card minor, 12-17hcp. 2nt only force. With 12-14HCP bid the minor. With 15-17HCP bid hearts to show clubs and spades to show diamonds. If responder bids clubs and that is not your suit you correct to diamonds. If responder bids spades, Pass (may raise to 3s with 17hcp)The advantage is you know 2 of the suits and the range and can place the contract with minimum risk. Disadvantage is opponents also know and it helps their defense. It is never used when you hold a 5 card major.