304 Bakin karfe Engbow shine bututu mai dacewa wanda ya haɗu da bututun guda biyu tare da diamita guda ɗaya ko daban-daban a cikin tsarin pipping, don haka bututun da aka ambata a wani wani lokaci. A cewar kusurwa, an fi amfani da shi shine 45¡. 90¡Ã, 180¡Ã. Bugu da kari, a cewar bukatun injiniyan, wasu sauran baƙin ciki kusurwa kamar 60¡ suma suna kunshe. Hanyoyin haɗin haɗin da bututun sun hada da walding kai tsaye (hanyar da aka fi amfani da ita), haɗin yanar gizo, haɗin haɗi, haɗin sodet, da sauransu.